American here and by no means an expert so take this with a grain or 1000 of salt. It’s not segregation (at least not enforced any more) as much as a cultural thing. Many black churches likely started during segregation and the culture has definitely shifted over time which heavily influences things like music (look up soul gospel or soul music) and I believe tend to be more colorful in clothing and decor. There are aspects of elements of a service, and without a doubt influences on the topic of the sermon (thinking about it… Sermon might be a very Catholic word so I am not sure if that translates well). There might be some social do’s and don’t’s that I don’t know of as well but I don’t have first hand experience