Racial differences are bullshit.
Cultural differences are real, passed on through generations often, and powerful. But they can also change quickly.
Stereotypical understandings about cultural differences are usually mostly wrong. But that doesn't mean that there aren/t extremely important cultural differences.
We (not just the US, but the whole world) used to have very ethnocentric (my group is best) views of racial/ethnic differences. The world also used to think that all ethnic differences were innate. (The truth is that they are all cultrual, and learned, but still of "inherited" quality, in a sense, by the teachings of parents to young children.)
Now the US and Europe have an excessively PC official view, at least, that there are no differences, other than utterly superficial and unimportant ones, between different ethnic / racial groups. That is also absurd. The cultural differences between different human groups can be very important, and under usual conditions, very durable. (They don't have to be durable, but they usually are, in most societies.)
Response to intellectually limited PC ranting. True racism is of course much worse.