Reality check: Buddhist Aztecs

Question

Idea

Is the following alternate history setup conceivable:

• Central Mexico has been converted to Buddhism by missionaries arriving from East Asia or South-East Asia hundreds of years before European conquistadors arrive.
• By the time of European conquest of the Caribian, Central Mexico is organized as a centralized and predominantly Buddhist state.
• The missionaries brought scriptures (naturally) and some knowledge of East Asian technology (advanced metal working, steel, the wheel, siege weapons, etc.).
• There is no continued political interference from Asia in the Americas, certainly no military interference.
• With the Pre-Columbian contact, Native Americans have acquired some immunity against Eurasian diseases.

Note that with a very different timeline, the people in Central Mexico would not be called Aztecs; I am just calling them that for want of a better universally understandable term. (In fact, they were not called Aztecs; this term is an invention of 19th century scholars.)

What it could look like

On Holy Thursday, the anniversary of the Last Supper of Our Lord, in the year of Our Lord 1519, the Captain-General ordered us and all his fleet to disembark in this strange new land. While we made camp between the dunes we noticed a shrine with a heathen idol nearby, a gilded statue showing a monstrous sitting figure with six arms and a serene if gloating smile. The Captain-General ordered the false idol removed and replaced by the likeness of Our Lady.

For some days, the Indians native to this country avoided us, until an embassy arrived on Easter Sunday. The embassy was led by an Indian of noble birth, Teuhtlilli, Governor of Cuetlaxtla, accompanied by many servants and warriors. Teuhtlilli brought presents of fowl and vegetables and greetings of the prince of this country, who was called Ahuitzotl the Enlightened. Among Teuhtlilli's people, there were several barefooted men with stoic expressions clad in nothing but an orange robe. We learned that they were heathen monks, learned in religion and all the arts and the Indians greatly valued their council. The warriors, on the other hand appeared in full metal armor, with lances and steel swords and steel helmets adorned with golden images of snakes and dragons and terrible monsters. They assured us that there were indeed fire-breathing dragons that inhabited the mountains of the lands ahead.

The Captain-General ordered an altar made. Fray Bartolome de Olmedo celebrated the Holy Mass in the presence of the Captain-General and his men and the Indian embassy, for the Captain-General wanted to show the heathens the way of the true religion. Afterwards, the Captain-General dined with the Indian ambassador. He also arranged a demonstration of the cannon so that the ambassador should see it fired. The ambassador was thoroughly unimpressed. He seemed insulted and demanded to know why we had defiled the shrine to the Bodhisattva Quetzalcoatl. The Captain-General tried to explain our holy faith, but Teuhtlilli would not hear it. He demanded that we re-embark and leave this country immediately; then he departed abruptly.

The next day, we learned that an Indian army had arrived and was encamped not far from where we had made landfall. They numbered in the tens of thousands, all with formidable armor and weapons made of steel. They also brought a number of trebuchets; one of our ships that came too close to the Indian camp was hit by a flaming projectile and set ablaze...

(Note that style and some of the wording and context is adapted from Bernal Diaz' account of Hernan Cortes' conquest of Mexico.)

How it could have happened

For a time, Buddhism was aggressively prosetylizing everywhere from Japan, to Central Asia, to modern Indonesia, to Egypt and Greece. An apparent Buddhist missionary who came with an Indian embassy burned himself to death publicly in Athens in 22/21 BCE to demonstrate his faith. Buddhist missionaries may have been government-sponsored but were happy to work alone, under hardship, and far away from their countries of origin. They would certainly have been willing to go to Mexico, had they known how.

There was speculation about whether Buddhist missionaries may actually have reached the Americas in Pre-Columbian times. Around 500 CE, a group of Buddhist monks traveled from China to a country called Fusang, across the sea 20000 li East of China. One li is between 300 and 600 meters (depending on where and when), which is not quite far enough to be America but much further away than Japan. Traditionally, it has nevertheless been interpreted to refer to some part of Japan or Sakhalin or other islands.

Further, in later times, it happened frequently that Japanese fishing boats were driven out into the ocean and across the Pacific. Some Japanese sailors survived and were taken captive by Native Americans in the 19th century. It seems conceivable that this might have happened in a similar way 1000 years earlier to Buddhist missionaries bound for Japan, China, or Korea.

Potential Problems

• While Japanese fishermen carry potentially enough food (or at least the tools to acquire some) for the long journey across the Pacific, a ship sailing the rather short way between Korea and Japan, or even between South-East Asia and Japan would probably not.
• Buddhist missionaries in other regions were most successful when relying on a network for ideological (perhaps also material) support. Buddhist states and Buddhist monasteries could provide that across Asia, but not in the Americas. Especially when considering that the missionaries would not have had any way of knowing where they are, how to get home or write home and report about their success, etc. Even with nautical knowledge, traveling reliably across the Pacific (in order to get back, even if you understand where "back" is), requires understanding the volta do mar. The Spanish had to try for a while and lost many ships before they got it right.
• The religious establishment in Central Mexico would not be amused.
• Technological knowledge is difficult to transfer. The Mongols for instance had to bring in Persian engineers to build counterweight trebuchets and reduce the Song fortresses. Buddhist missionaries may not be concerned with either steel or siege warfare or anything of the sort. Even if they had seen this in Asia and were willing to help by reproducing this technology in Mexico, they may not succeed. Or possibly they would produce very crude versions of it.
• The wheel may not be useful enough without large draft animals. But missionaries would not accidentally bring horses or water buffalo (or perhaps they would eat those when starving at sea).
• It may be impossible to move a trebuchet without draft animals.
• A one-time or two-time contact with a few missionaries may not have been enough to spread Eurasian diseases to the Americas and cause immunity to develop.
• Iron ore may not be easily to find in or around Central Mexico.

Answer 1

Yes, this could totally happen.

Essentially, three things need to happen for this scenario:

1. Contact - Some East Asian exploration of the Americas centuries before 1492.
2. Religion - Those explorers/missionaries convert the local population.
3. Disappearance - East Asia is no longer involved on the continent.

Let's take a look at each requirement.

Contact - completely plausible. Chinese explorer Zheng He reached Africa, and probably had the ability to travel further. In fact, the European explorers of the 15th century did not posses any uniquely advanced technology, the deciding factor was motivation (rising prices of spices). If for some reason China really wanted to sail east - they could do this.

Religion - the easiest part. Christian missionaries easily (and rapidly) converted the local population, Buddhism could do the same.

Disappearance - this is the least likely bit of this, but not impossible. Why would you leave a continent in which you are the only overlord. However, we are talking about China. Thorough the previous millennium they knew repeating periods of expansion followed by closing the borders and focusing on the internal affairs.

A (reasnbly) viable background story could be something like:

One Chinese emperor was possessed with exploration, his ships sailed east and discovered the Americas. Afterwards, the emperor supported the American presence enough to promote a technological, religious and biological exchange. However, his successors were extremely isolationists, and thus stopped all transpacific contacts. Then some crisis happened (civil war/Mongol invasion), and by the time the country became stable again the tales about the American escapades were seen as legends.

Answer 2

Why not have an even earlier point of departure? Genetic mapping studies by Cavalli-Sforza have shown a pattern of genetic expansion from the area of the Sea of Japan towards the rest of eastern Asia. This appears as the third most important genetic movement in Eastern Asia (after the "Great expansion" from the African continent, and a second expansion from the area of Northern Siberia), which suggests geographical expansion during the early Jōmon period. These studies also suggest that the Jōmon demographic expansion may have reached America along a path following the Pacific coast, via the Kuril Islands and Aleutian islands, and that the natives of the Pacific Northwest have significant genetic admixture with the original natives of Japan.

But this expansion, the 'Jōmon Exchange', happened too early on IOTL, and ended too soon, for any of the technological, agricultural and social developments which Japan picked up later on in the Yayoi period to make it across to the Pacific Northwest, or for any prospect of extending the Japanese branch of the Maritime Silk Route, which was only established c. the 4th-5th century CE. Contact wasn't maintained, and neither was maritime trade; as such, it took until the late 1700s for the Russians to establish the Maritime Fur Route, by which stage it was far too late.

So, why not have this maritime fur trade route established earlier, either by the Japanese or by the Pacific Northwesterners themselves? In so doing, the transmission of Buddhism to the Americas is via the Japanese branch of Silk Road, just like the trasmission of Buddhism to Japan was. During the fifth and sixth centuries C.E., merchants played a large role in the spread of religion, in particular Buddhism. Merchants found the moral and ethical teachings of Buddhism to be an appealing alternative to previous religions. As a result, Merchants supported Buddhist Monasteries along the Silk Roads, and in return the Buddhists gave the Merchants somewhere to stay as they traveled from city to city.

As a result, Merchants spread Buddhism to foreign encounters as they traveled. Merchants also helped to establish diaspora within the communities they encountered, and over time, their cultures became based on Buddhism. Because of this, these communities became centers of literacy and culture with well organized marketplaces, lodging, and storage. With this trans-Pacific branch of the Silk Route, via the Bering Strait, the merchants could easily have spread Buddhism to the New World in much the same manner as they did on the Japanese archipelago, with similar results.

Answer 3

Buddhists would be barred from Mexico by disease

Buddhism was expanding quickly in the first centuries AD. It spread widely in China in the 200s, into Korea in the 300s, and 538 to Japan. The most likely route for a trans-Pacific voyage by missionaries would have been by skirting the edge of the land, up to Kamchatka, across Alaska, and then down the West Coast of the US. These lands are relatively rich in food sources, and there probably would have been plenty of intervening groups for the missionaries to interact with.

Ultimately, trans-oceanic voyages were probably both out of the missionaries capabilities and too expensive even if they were capable. Firstly, the Chinese had very large ships, and did a bit of exploring under Zheng He (though that was the 1400s, not the 700s). But they did not have experience with open ocean navigation the way that the Europeans had. Spanish and Portugese sailers that embarked on the voyages of exploration spent a lot of time going to Azores and Canary islands and back, and there were Basque fishermen that went to the Outer Banks near Nova Scotia. The didn't regularly sail to such far away islands; the Phillipines is probably the longest over-water crossing that they Chinese sailors regularly made. To my knowledge, there is no evidence of Chinese or Japanese contact with Guam, for example.

The second point relates to expense. Trips to the Americans were sponsored by European crowns at first, then by rich merchant groups after ~50 years once the economic potential of the region was uncovered. China (or Japan) would not have had much economic use for the Americas at that Early point, and there isn't much suggesting the Emperors would be interested in sponsoring a lot of ship traffic. Buddhist missionaries were able to spread by foot easily to China and hitch rides to Japan, just as Jesuits and Franciscans were able to hitch rides to America with the Spanish. But barring other reasons to sail the deep Pacific, even if the Chinese or Japanese had the technical knowhow to cross, the Buddhist monks couldn't afford to pay for their own ships.

So lets limit the missionaries to the coast-hugging route across the north. Let's say a Buddhist mission made the Pacific Northwest and spent some time converting the totem-pole making, fisherpeople of the area. Communicable diseases quickly strike and over-run most of the population of the the Americas (as happened in real life). The large towns de Soto saw in the 1540s were essentially gone a century later.

The problem is that now the Buddhist monks lose their stepping stones to Mexico. A successful conversion experience (as seen in China) need a set of monks to move back and forth from the mother country to the newly converted territory, bringing rituals, written documents and translating them.

With the hunter-gatherer tribal areas from Alaska to California disrupted by disease, the links back to the homeland are broken. Further missionaries can barely make it through the wilds, and once sedentary tribes that provided shelter are disrupted.

All in all, I think there are several reasons to think that a Buddhist conversion of Mexico is unlikely, barring significant changes to history.