What I thought of first with the Native American population question was: Are they talking about pure-blood Native Americans, or people with some Native American ancestry? In remote parts of Mexico there are villages of pure-blood Maya people, but I'd be surprised if there are any Native Americans in North America without some non-native blood. They clarified it, however, by saying people who answered the census by stating Native American as their sole ancestry. Kind of wishy-washy if you ask me. Over the course of 500 years, the only way anybody is going to be pure-blood is if they live in a region so remote that there is effectively no communication with the outside. Such areas exist in Mexico. Not in North America. I picked that item as the fiction based on my own definitions, but it turned out I was right even on their definitions. I get SoF right far less than chance. Sort of like the Monte Hall problem, you'll get it right more often if you pick one of the choices I don't.
In this day and age, pretty much everybody in Europe and America is mixed race. I suppose that places like India and China have regions where foreigners have never been and races are unmixed. The eugenicists had it backwards: You can breed people, animals, and plants to be stronger and more attractive, but you do it by mixing races (hybridization) rather than by keeping pure strains.