I had a sociology prof. in college who was a hysterical (he thought the Bush I admin was trying to murder the Indians) advocate of immense Indian populations in the area of the present U.S. His "specialty" was/is N. American Indians, and he occasionally gets his articles printed in the local rag. He never presented any proof, and I've never seen any proof that Indian populations were any more than 2-3 million. No big cities, no huge stationary populations, no remains of millions of people.
I understand, but I’m telling you that even the numbers of the groups you mention have been steadily revised downward. My point is that TOTAL numbers have been moved downward decade by decade.