Don’t know; I’m neither a historian nor an archeologist.
However, as an example, “Squanto” was kidnapped from now-New-England in 1614, returned in 1619, and in his absence nearly the entire population of southern New England was wiped-out by an unknown disease, perhaps caught from the French explorers.
https://en.wikipedia.org/wiki/Squanto
https://en.wikipedia.org/wiki/Squanto#The_great_epidemic_and_Squanto’s_return_to_New_England
Unknown disease....unknown numbers
That really supports the death of sixty million. There should be bones all over the place