I'm not an American but I honestly have a single question:
What is black culture in the US?
Don't get me wrong, I will support anyone who celebrates their culture, as soon as the culture exists.
But you yourself mentioned "black pride" in the sense of "pride of people that are born in the US and raised in the US" and as far as I know, since those people do not have any ancestor traces to a specific country or tribe or cultural group, they only have one culture themselves: American culture. So in that sense, black pride is not really a celebration of heritage, pretty much like white pride.
To clarify it even more, I'm going to take as an example 4 imaginary people:
- Alan is a white man born and raised in the US. He cannot trace his ancestry and always considered themselves just an American. He has American Pride.
- Bella is a white woman born and raised in the US. Unlike Alan, she knows that her ancestry goes back to Italy, since her parents are Italians born and raised in Italy. Her family has Italian pride, and so does she. However, she has American pride too.
- Cory is a black man born and raised in the US. His grandparents however, came to the US from Congo. He knows his ancestry and this is why both him and his family have Congolese pride. He might also feel American pride.
- Dana is a black woman born and raised in the US. She is the case you mention, aka an African-American who cannot trace their ancestry to a specific country or tribe, since it goes back to slavery era. Since she cannot trace her ancestry, and does not have any cultural associations with anything from any tribe of black origin since both her and her parents were raised by the American standard, how come her "pride" is different than the pride that Alan has? Shouldn't her pride also be just American pride?
But here is the difference: Cultural prides, such as "Greek pride", "Irish pride", "Chinese pride" or "Hindi pride", all have to do with appreciating the "cultural particles" of your ancestral culture (that means the language, cuisine, history, art, music, dances, religion, clothes, etc). Black pride is not like that since black people cannot appreciate their respective cultural particles, since they don't know their ancestral culture. And you might say "but they are black, they are celebrating the cultural particles of black culture". NO. Seriously, that's pretty much racist since you consider all black people (including indigenous people of Africa) having THE SAME CULTURE. Which is far from the truth since there are hundreds, if not thousands, of different cultures, each one bonding onto a specific country, tribe, or cultural group. But if that's so, why is "Black Pride" still used as a term by black people themselves? This is because black people use it in the same way that gay people use the term "gay pride": they are not pride of the black culture. THEY ARE PROUD BECAUSE THEY ARE BLACK. Black, as in skin color. So, in a sense, it is pretty much the black counterpart of White Pride; aka it's a type of RACIAL PRIDE. It is definitely different however, considering how brutal White Pride supporters have been to people of other races, but I will ask you one thing: how do you know that one day in the future, Black Pride supporters won't do the same acts towards whites as whites did back in the days?
TL;DR: Dichotomy between "cultural pride" and "racial pride"