Europe is a great example, because it isn't actually counter factual. Yes, Europe didn't unify the way China did, but that doesn't mean Europeans don't share an identity.
The reality is, they are far closer to each other (and to their colonies) than they are to any other group. Hence the existence of concepts like "white," "European," "Western," etc. When push comes to shove, Europe will tend to unify behind a common banner, and their assimilation processes work best with - and historically assumed - other Europeans. This is why the US called its feud with Russia a "family feud" but its feud with China a "conflict with an entirely [alien] civilization." It's also why European and American leaders are far more okay with being "border less" with other Europeans, than being "border less" with Indians, Africans, Mexicans, etc.
The nature of Western political correctness is that, in polite company, they don't say what they really think. But we all know what they really think. Once you remove the blinding light of liberal ideology, people are indeed quite similar in their common tribalism. Language, race, culture - these are the binding principles of identity. Even within boundaries of entities (like historical empires) that failed to respect these principles, the identities persisted, and in moments of political weakness, they'd rise to the surface in explosions of violence, civil strife, and political disintegration. We've seen it all before.
