USAmericans have a heavy focus on heritage due to their history (wiping out nearly all of the local population). It is thus a great melting pot of people who left their own behind and had to start again from scratch. Going to another country where everybody’s from somewhere else led to them trying to find out how they’re unique and looks and heritage are the easiest to focus on. Combine that with a good chunk of their population being descendants of slaves (African, Asian, and European) and you will have a bunch of people focusing on that. Now factor in that blacks are the third biggest ethnic group.

The same didn’t happen elsewhere to the same degree as in the US because there are millennia of history and culture in other places or the population is more homogeneous. Go to Poland you’re surrounded by Polish people whose forefathers might’ve come from the very same region, spoken the same language, adhered to the same values and customs, suffered very similar fates, and shared the same traditions. They will try and stand out differently e.g through their accent, dialect, money, and so on instead of skin color and heritage.

It is a complex, multi-faceted issue, but those are my impressions of it. I agree that the focus is annoying, especially when copy-pasted abroad as if history doesn’t matter there, but I’m sure the more you read about US history, the more you’ll understand.