America was/is one hell of an experiment. 200 years of taking people in who left their own countries, and cultures to start over here.. And damn it if it didn't work. For 200+ years we got through all of the problems and historical fights and divisions and hatreds between religions, and nationalities, and races, etc. People actually lived together.. There were bumps, Civil War being one, but the experiment worked..
Lets hope now the hatred in politics we have today won't lead us to divisions so deep that they will be the end of us being 'exceptional'..