But what about states in the United States? They were explicitly formed as a set of states - nations - that cooperate under a federation. Free migration wasn’t always the case in the original states but was required in the constitution.

What about the EU? People can move about freely today when in the past they weren’t able to.

Or are you saying there’s something superior about Americans and Europeans and we need to keep everyone else in their prisons?

You quote 12,000 years ago as some sort of transition. Realistically migration was relatively unimpeded until the 1900’s. Citizenship isn’t the same as migration, and in many cultures citizens and denizens were two classes with the denizens migrating relatively unimpeded. Some cultures like ancient China had travel papers but that was reserved for nobles or elites - normal people were too beneath notice to require documentation to travel.