Why is America still so racist?

I swear, everywhere I go, there is racism. For example, I attend a very diverse college and I attend that college because I love to meet people from all nationalities and racial backgrounds. I have an African-American friend in one of my classes that I have known for years (were best friends), and I am white. Everyone in the classroom looks at us strange when we joke around because, obviously, were different colored. People in the class on multiple occasions have asked why he hangs around me and why I hang around him (yes we hear you racist bigots in the background lol). But you know, we don't plan on going are separate ways after 25 years of friendship. So why is it that people of different races can't just get along? I mean, it's everywhere, racism needs to end because I really enjoy people of all cultures.