What did the native Americans come from?

Um like tbh I dunno but here

The ancestors of living Native Americans arrived in what is now the United States at least 15,000 years ago, possibly much earlier, from Asia via Beringia. A vast variety of peoples, societies, and cultures subsequently developed.

and

Prevailing theories suggest that Native Americans are descended from a group of East Asians who crossed the Bering Sea via a land bridge perhaps 16,500 years ago, though some sites may evidence an earlier arrival.

this is a good question! i'll do some research and come back when i have the answer!

the roman empire began to fall