So let's erase all borders and see how we get on.
Orwell: 'men can only be highly civilized while other men, inevitably less civilized, are there to guard and feed them.'
That'll be the same France that has nuclear weapons?
Now consider how many people are hurt every year over enforcing laws that have just as imaginary lines drawn about other issues. Things like not being able to vote because of an imaginary line. Not being able to buy alcohol. Being forced to go to school where you have no rights to protect yourself from being harmed.
Those imaginary lines drawn on soil determine how resources are allocated, for example, enabling cheap energy and customers for the US’s military industrial complex, or cheap spices and labor for the British, and so on and so forth.
Even the most advanced mammals use tribes to maximize chances of survival, and humans are no different.
Yes, that happens when ethnic cleansing is completed so that what were previously multi-ethnic empires are now mono-ethnic nation states.