nations in america are the englisch speaking, the hispanics, the sioux etc.
Probably many people with disagree with you because USA has a feeling of a nation. I think this is mostly due to wars. If you are a nation and fight a against a common enemy, it will unite the people. First against the British, then WW1 and WW2, Korea, Vietnam, Iraq 1&2, Afghanistan. With so many foreign threats, there should be a lot of unity. Unfortunately all of this is being lost in the last few years.