I live in a state where vast tracts of it is reservation land. The natives that got the land in my state were only active in this area for a few hundred years; they took it over from another tribe that held it for like 1000 years before that. But because they held it by the time colonists discovered the land, they ultimately got claim of dominion and are now the tribe associated with the land. Meanwhile the actual original tribe that held it for a millennia got nothing.

Ultimately a lot of "native land" in the US is an arbitrary distinction since tribes only vaguely understood and enforced the concept of property rights and due to their nomadic nature never were indigenous to any specific land. Present-day land claims are based on observations of land ownership at the time of contact.