[Fraxinus]

You are comparing numbers for after the tribes you mention lost in excess of 50% of their population due to epidemic diseases. I also have severe doubts that the agriculture practices of the early American Republic were an order of magnitude more productive than that practiced by the Cahokians. There is also extensive, but often ancedotal data that there was significant reforestation in the perion of 1500 through 1600. This was formerly cultivated fields that were alowed to change to forest and were not cut down and returned to annual crops after a long (15+ years) fallow period. The long fallow period is often used in slash and burn agriculture.

[Antoninus]

You are comparing numbers for after the tribes you mention lost in excess of 50% of their population due to epidemic diseases.

No, I'm not. In 1615, these tribes hadn't been struck by the dread diseases yet. That would happen in the 1630s.

I also have severe doubts that the agriculture practices of the early American Republic were an order of magnitude more productive than that practiced by the Cahokians.

Ever read any of Jefferson's writings on the subject? Fairly sophisticated if you ask me.