That's easy. Because it's only majority white cultures that have been taught for decades to hate themselves and their history.
This isn't about making sense or doing what's logical; this is purely about catering to irrational emotions. I mean, to Hell with worrying about socialism at this point; our society is so self-loathing that we don't even have to change the structure of our society to be weak.
Slavery is still flourishing in many different forms all over the world - wage slavery, mental slavery, medical slavery, oppression under totalitarian regimes/religions... When free will and individualism is crushed you have slavery. And the focus is on the US, because it has stood for freedom and liberty, and authoritarians need to destroy that to take power