There is this movie, it's called America, America....
It was written and directed by Elia Kazan and is loosely based on his Uncles long journey from the Ethnic fighting in the old Ottoman Empire to his version of Eden, Ellis Island.
This is what it's all about, the true meaning of America, the idea of it keeps us together. There is no tribal or clan ties that defines you, brands who you are. That is what makes this country unique. The idea of America is what gives this Country of ours it's unique.
Of course there is all sorts of restrictions and barriers to jump over but in the end, what keeps us together, what gives us a national identity is the Constitution.