I'm from east Europe. In my country there have never been black slaves. There have been white slaves. The rich would sell the poor as salves to other rich people.
However if I wanna be proud of being middle class white person today, that would raise a lot of eyebrows and not a few people would assume I'm a "white supremacist". You cannot be proud of being white. Doesn't matter what your country history is, or what your personal context is.
My hypothesis is that American history has been conflated with "white" history so now all white people are privileged and oppressed black people and have no reason to be proud.