That’s a hilarious assertion. One of the things we found puzzling when we moved here was why Americans spent so much time in school studying all the bad things the country did. Totally bizarre to us, coming from Asia.
I’m making a different point. The idea that Americans whitewash their history is absurd compared how kids are educated in nearly the whole rest of the world.
I don’t have any issues with teaching about American history and things that were done that were wrong (in hindsight or at the time).
But what you might be referring to is this bizarre self-flagellation that has grown in popularity which focuses exclusively on the errors and ignores any of the good things about America.
My personal opinion is it’s because the people doing it want to remake America - throw away the old and create a “more just” society (obviously following their politics).
If you can use this self-criticism to destroy the foundation of America (through association) you can get rid of those pesky ideals preventing you from transforming society. Things like individual freedom, personal responsibility, inalienable rights, judging the individuals by their own actions and not the sins of their ancestors, etc.