Addressing the education portion of your question, I grew up in the American South in the 1980s-90s, and I learned plenty about the horrors of slavery and Jim Crow in school. I recognize this is a single data point, but am pretty sure these are widely taught. I also don't really hear anyone calling for a return to slavery or Jim Crow, so this education seems to have successfully imbued our culture with a sense that these are bad things.

I think your overall question is answered somewhat by the fundamental demographics of each country. What percentage of Germans today are ethnically German? A lot. In the US, our racial mix is much more fragmented, to the point where racial minorities have thriving subcultures that some people don't view as extolling "traditional American values," whatever those are. But these subcultures are increasingly visible and powerful, leading to resentment among many who view their culture, that of "traditional American values," as losing power.

The single largest ethnic group in the US are people of German descent (I'm one of them), with well over 40 million people, and these people along with people of British descent are largely the ones driving this "traditional American values" bullshit. People of Irish descent used to be subject to serious racism in the US in the early 20th century, but have since been fully accepted into the dominant white culture and many now also participate in white racism against Black and Hispanic people.