I'm wondering why you think it's strange that Americans would care about the conditions where they live. Black people in the United States deal with the negative consequences of slavery every day. White people who crave social justice work with Black people to make our society a better place.

We don't crave a society that's as just, more just, or less just than other societies. We're working on our own society, because we live here.

That should not be all that difficult to understand.