You might have given just the reason why United States of America is losing its strengths. Correct me if I am wrong because I don't know the time before I was born. But even in couple of decades ago it was rare to hear someone say I am African-American, Italian-American, Irish-American, Mexican-American, and Chinese-American and so on. You are either American or else. This whole generalization of people in the country of USA is more and more look like country is being divided inside. What you are saying is. Yes, we are all Americans on paper but we are Dominican, Italian, Irish, Chinese etc.. first. I know you can't change your color of your skins or ethnicity but where have those "I am American and I am proud of it" kind of mentality go? Yes I do have Italian-Irish and probably other blood mixture in me but I don't go out of my way to say I am Italian-Irish-American-Mut.
The United States of America started as a melting pot but it's now more like a sancocho. There is a common sauce that takes from all the ingredients but you can also taste the individual ingredients separately.
There are the common values we all share and those are the most important things, freedom and all that, but we can still notice and even celebrate our differences. I don't think it makes the US any weaker or its citizens less patriotic.