Actually, the indigenous cultures in the Americas -- and I'm specifically refering to North America here -- had a very advanced culture prior to European contact. I will refer you all to the Anasazi, the Pueblo, Cahokia Mounds, and the Mound Builders in general (e.g., Serpent Mound in Ohio) as examples. The date for human occupation in the Western Hemisphere is being continually pushed back, especially as underwater and other archeological surveys are done on the coastlines of of the Pacific Northwest regions.

It's now thought that one of the major factors in the extinction of the mammoth in North America was hunters.

You and I probably could not survive in their world. I suspect that they could easily survive in ours.