In this alternate scenario, man created the bow and arrow BEFORE leaving Africa. From what I had read, this can result in many technological revolutions while the Earth was still in the grip of an ice age. So man used horses, elephants and camels as draft animals, built the wheel and began writing before the climate chaos that is The Younger Dryas.
The basis of this question is that while the Old World basked in the glories of Egypt, Rome, China and Japan, the Americas had very few evidence of civilization. The following evidence is as such:
In OTL, the reasons settlements like these were not so common in North or South America is that they did not have the pack animal or the wheel. If man became archers before leaving Africa, maybe the pre-Columbian Americans could have plenty of both. These two could potentially result in empires with a scope to match that of Rome or at least Ptolemaic Egypt.
But this raises yet another problem. In North America, there are 562 federally identified Native American tribes and perhaps as many in South America.
If the Native Americans did have the tools and technology to build empires large enough to cover good portions of either North or South America, would the number of tribes still be the same? Or will mass empire-building drop that number to a noticeable degree?