Suppose that a traveler left the Roman Empire, or China, or India, or the Caliphate, or some other advanced civilization, and traveled to a different society. They could travel to societies classified as barbarians or even as savages as far as their technology or social organization went.
Do you remember reading The Hobbit (1937) as a child? I read it years before reading The Lord of the Rings, so for years all I knew about Middle-earth was what I knew or could deduce from The Hobbit. As Bilbo and the dwarves travelled east into a region called "Wilderland" or "The Wild" things became a lot wilder and less civilized.
Here is a link to a site which has a copy of the map of Wilderland from The Hobbit.
https://tolkiengateway.net/wiki/Map_of_Wilderland#/media/File:J.R.R._Tolkien_-_Map_of_Wilderland.jpg
And I noted how, shortly before they met the trolls, they said that people in those regions had "never heard of the King".
So I deduced that somewhere in the west beyond the borders of the map of Wilderland there was a "Tamerland", or a "Milderland" which included Bilbo's homeland. And I suspected that there was a large and powerful and peaceful Kingdom that probably included where Bilbo and the Hobbits lived and the home of Thorin's exiled dwarves.
And apparently as you travelled east the control of that kingdom got looser and looser and more and more wild creatures in habited the land and did what they pleased. And to the east of the mighty kingdom's gradual borders there was only anarchy and tribes of wild people, except in Rivendell, the Elf Kingdom in Mirkwood, the Lonely Mountain (once Smaug was gone), Laketown, and the Iron Hills, and possibly in the lands that the Wood-Elves traded with.
As it turned out in The Lord of the Rings the kingdom in the west had fallen a thousand years ago, but people still remembered it a little by saying that evil beings "had never heard of the king".
I also noted that in The Hobbit evil beings seemed to come from the North.
So I noticed that in The Hobbit the north and the east seemed to be the directions of evil and things seemed to be worse in those directions.
And that seemed strange to me, a kid in the USA. In US tv shows and movies the opposite was the case. The north and the east were the directions of relative good, of civilization and peace and safety. And the south and the west were the directions of relative evil, of savage violence.
The south was the region of the rebellion against the US government in the Civil War. And the west was the region of lack of civilization and of wild violence from hostile Indian tribes and evil outlaws.
And that was actually pretty much the historical situation.
I remember reading about 19th century Indian campaigns in the middle plains regions by a reporter who covered them. As he traveled west he travelled through regions which were equally civilized. But after he crossed the Mississippi civilization diminished the farther west he went. St. Louis, Missouri was the 4th most populous city in the USA in 1870, with half the population of Philadelphia and a third the population of Manhattan. And the farther west the reporter went by train and stagecoach the smaller the towns and villages got and the less settled the land was and the greater the probability of encountering hostile Indian warriors.
In the 19th century most of the Indian tribes and nations west of the Mississippi were much less civilized that the rest of the USA. Many tribes relied on hunting and gathering for all their food. Many others depended on farming for much of their food but also hunted and gathered a lot. And other tribes were primarily farmers, like most white Americans.
Some groups in the arid southwest dug irrigation canals to water their crops. But the plains the level of civilization had taken a downturn. Many southern plains tribes relied on farming for a major part of their food. But when horses were introduced to the nomadic hunting and gathering tribes on the plains, they could now hunt a lot of buffalo and feed themselves well. So they flourished and multiplied and their warriors raided the sedentary farming communities.
The French in the Mississippi Valley armed tribes with guns and sent them to attack the tribes on the southern plains who were a buffer for Spain. The Comanches moved down from the north and attacked the southern plains tribes, almost exterminating the Plains Apache.
So the level of culture on the plains suffered a sharp downturn in the century or two before the western Indian Wars.
The tribes in the west had almost no metallurgy. They could beat iron into spearheads and arrowheads. Traders who sold them muskets and gunpowder also sold them lead and molds for making lead balls. They could heat up the lead and pour the liquid lead into the molds to make balls for their guns.
In the middle and late 19th century breechloading rifles and carbines were introduced. Some repeating rifles and carbines had magazines containing several cartridges so they could be fired several times without reloading. Indians also acquired those improved guns.
Those rifles used metallic cartridges which were preloaded with the gunpowder and with the bullets. And those cartridges were much more expensive than gunpowder and lead.
So the Sioux invented a process to reuse metallic cartridges, saving every used one that they could. They would load the empty used cartridges with gunpowder and with lead balls they made with their molds.
That was quite inventive. But on the other hand lack of knowledge of chemistry caused many Sioux to waste a lot of time trying to turn the black sands of Powder River into gunpowder.
And the west was rather savage in the ethical sense. The Karankawa tribe of Texas were reputed to be cannibals, though many believe it was propaganda by their enemies. The last Karankawas might have been exterminated in an attack in 1858. Another Texas tribe, the Tonkawa, were also reputed to be cannibals. They were moved to the Indian Territory. In the Civil War they supported the Rebels, so a group of pro-Union tribes attacked them in the Tonkawa Massacre of October 23-24, 1862, killing about half the tribe. Some reports say Comanches roasted the Tonkawas alive.
The Pawnee practiced occasional human sacrifice. White Americans and progressive Pawnees eventually convinced the Pawnees to end it after the one in 1838.
Many tribes had warrior cultures, where the only only way for a young man to gain wealth was to steal from other groups, and the only way for a young man to gain reputation was to fight against other groups. So each warrior tribe was in a constant state of low intensity warfare with all their neighbors except for their few allies. And anyone living within raiding distance of a warrior tribe could be attacked at any time.
So the USA is an example of an advanced society which contained many regions which were much less advanced, and where the local governments were, to say the least, not very obedient to the central government, and where violence was common.