A lot of this is a product of harmful influences on the culture. The phrase 'African American' only exists because for over a hundred years we used 'Black' and 'Negro' and other words as negative. Now it's *great* that the younger generations (like me, and probably you) are comfortable with simpler words because we can say them without malice being meant or heard. America wasn't always like that -- still isn't, in lots of places. 

So when she's like "Hey, come on, can't I just be an American?" That's indicative of social progress that's happened since Oprah was her age. When Oprah was her age, saying that would mean 'I'm turning my back on black culture,' in a time when that's all anybody wanted a famous black woman to do. That used to mean giving up. Now it means something different -- but those wounds are still going to feel fresh for a long time.

Anyway that's just one ignorant white guy's take. I don't know what I'm talking about, just tell me the thing I have to say that makes me not sound racist, and I'll go with that.