It's not as bad as it looks on tv! Black people are a hugely important part of American culture and the object of love and admiration across a lot of different sub cultures. The immigration and law enforcement officers you are talking about are very likely to be African American themselves.

Yes there are some places where the inner city conflicts with the suburbs and its surely a racial situation but that's an isolated phenomenon and is unlikely to come up on your trip.

Enjoy the states and if you are going to make it to Chicago hit me up :)