I hate that PC term.
If “American” means of the USA, those peoples are NOT “NA” due to ethnicity or even being in this region. The USA did not exist when their tribes were running about.
As well, what do they call these peoples not in the USA, or North America, or south of the USA?
They are aboriginal, or indigenous. Too bad if that offends.
Not exactly. Anthropologists think they're descended from migrants tens of thousands of years ago from what is now Siberia (isn't that Asia?) over a then-existing land bridge into what is now America.