> The whole concept of nationalism and border sovereignty has been with us for essentially all of human history,

Quite the opposite. The modern concept of "border sovereignty" as intertwined with the nation-state is a Westphalian construction. (Students of world history will recognize why this timing is not a coincidence). And even then, they didn't exactly catch on immediately.

Sovereign nation-states are a tiny piece of human history. They're not even the majority of recorded human history.