100M is on the high side of estimates of pre-Contact population levels, and metal working was not yet in vogue. Groups like the Aztecs were working copper and precious metals, but stone tools were generally in use elsewhere. That doesn't mean that groups weren't highly developed.

The Mayas were adept astronomers, with a calendar even more accurate than our own,and along with a mathematical system that included the concept of zero and writing, together with monumental architecture. Similar systems were in use throughout Mexico,Central America, and much of South America.

There were large cities in many areas, including some in the United States, like Cahokia,near St.Louis. In many cases,disease spread in advance of Europeans making the first contact with many groups, and population levels were already declining.

Agriculture was well developed throughout the Americas. Native American groups first domesticated maize, and tomatoes, among others - plants that were readily adopted by Europeans.

What was lacking were wild precursors of any critters suitable for domestication like the horse (alpacas and llamas were rather palid substitutes), very unfortunate when Cortez came calling. At first the Aztecs did not realize that the horse and rider were separate entities, although they learned fast.

The Aztec capital, Tenochtitlan, was larger and cleaner than any city in Spain, according to the comments recorded in journals kept by the Spanish themselves.

And yet human sacrifice was common, and justified by the internal logic of their religious system - so who is "civilized" and who is "barbaric"? If you ask me, we are all just dreadfully, and unpredictably, human....

I am not a college professor, nor have I played one on TV. I have stayed at Holiday Inn a couple of times, however...