I have wondered about that. In watching TV advertisements it seems the percentage of black actors is well above percent of the published population - 13% - ditto that for movies on screen and TV.
You bring up an interesting observation. I think it comes from the history of slavery, and more recently the memory of Jim Crow that has liberal Hollywood carrying guilt around like a millstone. They need to just let it go. We’re a majority white nation, it’s okay to accommodate the culture of white audiences predominately.
Entertainment companies in countries across the globe accommodate their dominant culture; and more importantly, their audiences expect to see their own in commercials, movies etc. That’s okay. It’s normal, people feel comfortable around folks that look and speak like themselves. It doesn’t mean they’re racists.
So, Hollywood leave your white guilt obsession at home. You don’t need to constantly force feed audiences other cultures; purge your guilt on your own time.