I also don't recall there being lines

And many more tribes and communities were outright murdered by colonizers before they could even be documented. There are plenty of tribes that are just lost to time or we know nearly nothing about because they have no surviving members.

Indigenous peoples also don't necessarily view tribes, nations, etc as rigid categories where you're either one or the other, no exceptions. That in fact is the European view where you can only be part of one empire and where every empire seeks to capture as much land and resources for themselves as possible. You'll notice that the native-land.ca map has tons of overlapping territories.