I lived for many years in a majority-black neighborhood in Detroit, and I wholeheartedly concur with you about not understanding Black culture.
You don’t know what you don’t know until you learn that you don’t know it … to badly riff on an idiom.
To think I lived for most of my life in the United States without having the foggiest idea how black people actually talked, cooked, romanced, mourned, partied … you name it.
Our society is racist because of how separate it is. People are racist because of the racist society we grow up in.
Not everybody can do what I did and move to a black neighborhood to learn culture. (which by the way, I moved to a black neighborhood for entirely practical reasons and not altruistic ones.)
But I think we can all try harder. And I agree with you, watching TV shows and movies is a great start.