This is ignoring the concept of "cultures" entirely. Other cultures are not the same as mine. They do not hold the same values, morals, beliefs or language. These are all important for societies to function.
Societies that are split along these lines are doomed to fail. Take a simple example of a new neighbor moving next door to you. If they don't speak the same language, do you think you'll form much of a relationship? Possible, yes, but more likely no. Now add religion, tradition, etc into the mix.
The idea that you can mark a map and define property and consolidate identities to property is so anti-human.
If you embrace humanity then you should also reject the premise that there is any Other humanity.
It's historically supremacist.