One of the real problems we have had with this stuff throughout history is that the very concept of "nation" or "country," with fixed borders, is not universal. In the past few centuries, colonial powers or imperial powers all over the world, from many cultures, have gone into tribal areas and carved "countries" out of them. Left to itself, the natural size of a nation is very small, like a state in the U.S. Look at these maps. this reference shows the initial form of Europe. Note the tiny kingdoms in the early years. Note in the 900 AD maps that many areas don't even have firm boundaries. China, Africa, the Middle East, were all like this, and they were all chopped up or mashed together into artificial boundaries, either by outside forces or internal kings, usually with no regard for the natural tribal boundaries. Pakistan. Palestine. Israel. Most of Africa. I'm sure you can think of dozens of other examples from every continent.

Many people adapted to this. Many others never did.

I think that this is a big source of many of our world conflicts to this day, and unfortunately there is no real way out of it. You can't turn back the clock.

Am I saying that we should have all stayed as primitive tribes? No, but given a more natural evolution, maybe there would be a lot more loose confederations, like the original United States before Washington became the overriding power over the individual states.