The two issues in America are not in practice totally separable. The relationship is not purely correlative. It's pretty clear in America that white people don't like to see some races "getting above their station" by climbing the class ladder. A pretty clear example are the Tulsa race riots: https://en.wikipedia.org/wiki/Tulsa_race_riot

Greenwood was a prosperous black area near Tulsa, doing so well that it was known as "Black Wall Street". White resentment eventually boiled over and 35 blocks were burned to the ground. Hundreds were killed, and it included many horrors, including white people using then-new airplanes to firebomb the neighborhood from above.

If you read Loewen's "Sundown Towns" you can find plenty more incidents where white resentment of black success led to oppression, violence, and sometimes death.

I'm not saying it's because of race -- if I wrote it that way then thanks for the correction. It just happen to correlate strongly with race. I don't know the underlying cause is and your hypothesis is close to my own. I mainly wanted to emphasize my own blindness to this trend because I had benefited from it.

I'm in the same boat. Its easy to just accept folks in roles without thinking about it.

E.g. I'm naturally gregarious, will chat up folks in line at the gas station buying a Coke etc. I noticed one day I didn't chat up anybody that didn't look like me. So I started.