Cultural lines are extremely blurry. I have more in common with a black person from Detroit, than I do with a black person from Maryland, Louisiana, or Texas. That doesn't mean our broader culture similarities don't or can't overlap. When you look at places in Africa, or the Caribbean and then cross them with certain elements of the American south, you see that cultural overlap with regards to certain foods, dance, music, and even language with the Gullah people of South Carolina.
On the other hand, when you travel especially to places with broad interest from places around the world(tropical vacation spots), or you go to live in another country things change very, very quickly, and you begin to understand the similarities we share with white people when you're seen as simply "American". Of course there is nuance, and because of our internal differences we ain't always gonna get along simply because we're from the same place. But shyt I was just in the DR, and these two complete strangers both from Texas...One black, one white got along like they knew each other their entire lives, just because both were from Texas, and could identify culturally with each other.