I take into consideration the fact that most historians are liberal and have an agenda. But after reading various articles about this subject on the internet, even after decades of contention, it seems most historians believe north of the Rio Grande there was maybe only two or three million pre-Columbus inhabitants. Central America was more conducive to population growth, and of course the Aztecs and Mayas did have cities where populations could build. But fifty million people at one time in Mexico? There’s absolutely no proof of that.
The American Midwest had the ability to support vast populations and did so.
Corn is a wonderful food. So is squash. So is the bean!
Brazil had vast areas under cultivation. The Amazon jungle hasn't always been jungle. Current research demonstrates that the populations in the Americas were far greater than imagined by earlier researchers who simply didn't have the tools to do the job.