I dont have an issue with 20 million, Cahokia, Double Ditch and many other sites have shown that stone-age cultures did congregate in very large numbers. Now to try to prove a number like 100 million is in my educated opinion, just absurd. We would need to identify another 100 sites on the scale of Cahokia to even be certain of a number like 20 million.
The 100 million number usually comes up in discussions of the entirity of North America ~ not about just the East Coast!
You say you don’t have an issue with 20 million, and then you to cast a skeptical eye on the numbers. There is no evidence anywhere in the world that would corroborate that stone age cultures like those north of the Rio Grande could support anything like the population density required for 20 million. The level of technological advancement and culture of N. American Indians was similar to that of Australian aborigines and the San of S. Africa.
The people promoting preposterous numbers are trying to get cultural and political leverage by inflating numbers just as “Afrocentric Scholars” have in connection with the slave trade to be able to play the “Holocaust card”.