Go back and read that link. Esp the bit where is quotes a couple guys who call the high numbers questionable.
Note also that the vast majority of those populations appear to be placed in the warm bits of Central America and the extreme South of North America. "The Americas" = all three continents.
Probably more relevant is "The aboriginal population of Canada during the late 15th century is estimated to have been between 200,000[10] and two million,[11] with a figure of 500,000 currently accepted by Canada's Royal Commission on Aboriginal Health."
That's not very many people spread over a very large area, and, like as not, the largest numbers, were in areas capable of supporting their feeding year around, either the East or the West coasts. There simply never was the food density to support any huge numbers elsewhere.
Like so many things, the predator/prey relationship plays out, and if you become too efficient a predator, you run out of prey really quickly and either starve or move on.
Or, as happened in my area, a rockslide shuts off the salmon run, and starves out the populace, and the area remains essentially empty, for a period of several hundred years while the stocks recover.
In this case, it certainly does not bode well for the game populations.