I'm not white so I can't speak of a "white culture", but when I think of "Black Culture" I think of generationally brown Americans of African descent.
Individuals can be brown Americans and not relate to Black culture because of factors like adoption, personal preference, etc.
When I think of Black culture, I think of generationally brown Americans who have (great grandparents), grandparents and parents from different socio-political eras of America. A pass down of Black Southern/Northern culture, cooking, humor, mannerisms, music and linguistic expression. A pass down of ways of thinking and looking at other races and cultures and the world. A pass down of hairstyles, and hair styling specific to the versatile nature of black hair. A sharing of a distinct history and curiosity of one another and of other brown people of different ethnicities but shared history (with the exception of some parts of Africa e.g. Ethiopia). An intersect and culture share with many Caribbean blacks, especially, for some reason, Jamaicans (especially 1st generation Jamaicans) A pass down of rhythm.
Humor (and story-telling) is distinct, and so is the intense soul borne of generational suffering that has shaped insanely talented musical expression and singing ability (see the connections between contemporary R&B then back to the Blues then back to Negro spirituals during slavery.
There are many negative behaviors that some individuals attempt to celebrate and integrate as the culture, but I, personally, reject that.
That is Black culture. For those who question its existence, I posit that they are not of the culture.
Though. You make a lot of awesome points, and I do believe that it is the clinging of certain aspects of culture aka repeated ways of interacting with the world that has always and continues to be part of the problem.