What happened to the Africans who were brought here and enslaved for generations has a long tail. Generational damage was done. When you take a group of people who because of the color of their skin are easily identifiable, and put them in a new country, enslaved them, treat them brutally, separate them from their culture, their religion, and their families, the scar exists for many many many generations.
This was not ancient history. It was 175 years ago, that these people were set free, pennyless, abused, and completely torn away from their original culture and religion. It is very important that Americans know their history and how we ended up being who we are.