Let's not pretend it's only Americans who have a case to answer. Many European countries were also guilty and/or complicit. That slavery has existed in many cultures in no way excuses it in any of them.
If Russia isn't implicated in this particular crime, there are plenty of others in its history which either its government or its people remain in denial about. Meanwhile racism is openly tolerated there, as I've seen and heard with my own eyes.
I love (and I think have a reasonable understanding of) Russians and Russian culture, but this is one area in which they could do with catching up with other countries.