Why are Americans so overly Politically Correct?

I was talking with this woman at GMU about a DSST test that I had given to a young woman at the Admissions Office front desk when the woman I was talking to asked me for her name I said "I did not catch her name, but she was a young black woman sitting at the desk"

The woman replies "Sir that's not really PC".

So I said "Well Ma'am i'm sorry that you feel that way, but I can't help the fact that you have a problem with black people being black". (The woman who I was talking to was black).

What I can't get over is "why are Americans so sensitive"? Your black, i'm white, she's Persian, these are all descriptions of what we look like not who we are. Yet it seems like so many Americans are afraid of offending or being offended that we forget "Hey if you have a problem with your race, if you're a little touchy about being called a black, white, or Persian woman, that the problem is not with me describing how you look but with what you perceive to be the characteristics associated with your race". By trying to forget that there are colors and races, Americans allow for racism that does exist on all sides to persist. What is important is that we are all Americans and share variations of an American culture. If we want our color and our race to not be important anymore, and a cause of discrimination, than we have to stop making our color and our race important.