Here's the problem. Throughout much of American history, minority groups, African Americans in particular have been considered a sub-class- not even counted as full people in the original constitution. This has two effects. First, it means that many accomplishments that would be noted as historical accomplishments for anyone regardless of race, were overlooked- often intentionally. Consider if you made textbooks for schools in the 1950's. If you list a great number of accomplishments of African Americans in your history books, how do you think your sales would be in the old south? Additionally, when prejudice was rampant, the population was not as interested as a whole in minority accomplishments because they couldn't "relate" to them or would not look to them as heroic examples. So many were "conveniently" forgotten. The second effect is that the value of accomplishments of minorities, especially those from groups who have been treated poorly in American history is remarkable. It is easier to make a great sacrifice or work toward a great accomplishment when you know your sacrifice will be remembered or your accomplishment heralded. It is also easier to give more when you feel a sense of appreciation for all your country has given you or done for you. African Americans and other minorities have not frequently had these advantages. Often when they made sacrifices or achieved great things, even things as simple as serving in the military, they did it with the knowledge that most of the nation disregarded them at best, and despised them at worst. During WWII black American soldiers fought and died, only to return to a nation, especially the south, where they could be subjected to lynchings, segregation, and open hostility with little reprieve from the government of their country. I heard one WWII vet's story that they had brought German POW's back to an American military base and were assigned to guard them. On several occasions they had to take the prisoner into town to eat, and while the German P.O.W's were allowed to go inside, the African American soldiers were forced to stay outside. To sacrifce for a country that has treated you that way is an accomplishment.
It has nothing to do with saying "what a great achievement for someone of your skin color", it has to do with "what a great achievement for someone facing so much adversity". And African American accomplishments today, while not free of adversity, are in my opinion worthy of celebration primarily as an example of our progress toward a nation united in its humanity.