Short version: “Native Americans” were the last migration to America. After they arrived, they murdered to extinction the earlier immigrants from Europe, who had arrived thousands of years earlier by following the glacial shore in small boats from what is now Spain to what is now Canada, hunting fish and mammals as they came in small groups in short steps.
Were these Euro-Americans so helpless? Did they not have weapons to defend themselves, or were they used to an Eden-like environment so they became easy targets?
Likewise, "they" murdered to near extinction earlier south american immigrants from Australia.
We have archaeological evidence as well as DNA evidence of those populations.
Every time one reads these threads about the origins of one group or another, what is generally overlooked, is the the successful group, killed all of the other group that they could get their hands on. Early humans do not appear to like strangers. So the first groups to North-South America appear to have “displaced” the earlier settlers. And it also appears to have been true in Europe-Asia. IMHO