Your scholarly research has produced an understanding that generally accords with my own. The Native American civilized societies seem today to be revealed by archaeological evidence to have collapsed ~1000 AD. The remnants of those civilized societies then were infected with diseases from Columbus and his crew that they had no immunity from, and therefore suffered up to 99% of their populations to have died of these plagues. It was that pitiful few remaining that European colonists faced and displaced from their ranges across N. America.

I was indeed pointing out that Denisovans were already present in N. America when the forebears of the Native Americans arrived, as you correctly ascertained.

The polities of Asia from East to West have arisen and been displaced by competing peoples over and again, for tens of thousands of years. Certainly the ANE have contributed during those millennia, both to the East and the West, and that heritage we share. When we look back far enough, all men are brothers.

Thanks!