Far from it. Concept of "country" or a "state" are way less artificial. Up until 1924 USA welcomed almost anyone with any background. Many countries don't care about it today. Australia was populated with literal criminals.

The concept of a "state" and its borders is to determine where its laws apply to. Historically, there was rarely even resources to mark the boundary in any meaningful way. But the problem of two kinds claiming sovereignty over a territory got resolved pretty easily -- whoever has the ability to collect taxes (aka tribute). Immigration was not a major concern at all. If anything, a feudal was more concerned of their tax base moving OUT of their jurisdiction, not preventing movement IN.

As I said above, Spain just gave permanent residency to everyone "overstaying" the visa. Does the concept of Spain as a country stopped "meaning something"?

> The US lets the most people in legally in the entire world, and by quite some measure[0]. If you think it's some xenophobic nightmare of a place then that seems an extremely narrow understanding of the world and the US's place in it.

USA immigration process is very hostile, compared to almost any other country in the world (IMO only UK and Switzerland are comparable). I went through it, as well as in other countries, can compare. Why are you so sure I have the "extremely narrow understanding"? Even paying $700+ for just one form, without any guarantees or money back is already sus.