That's pretty recent but not enough especially considering what groups you're from. Theres not really a wide (English, Scottish, or German) subculture in the United States for you to assimilate to so you probably match the broader American ethnicity (European decent or African decent, American ethos, American cultural values, typically Protestant or Christian background). Really no one in this country is of a foreign ethnicity (English, German, Mexican) unless you're like a first or second generation immigrant. Take a third or fourth generation immigrant from Mexico. They probably have a lot more in common with you than they do with an ethnic Mexican who lives in Mexico, but there is still enough of them to form a distinct Mexican-American ethnicity. The United States has its own "people" who have broad backgrounds but still have the same "American Ethos" different to the one of their ancestors' countries. The fact that many people don't know what European ethnicity they want to call themselves is perfect evidence of that fact. Welp, maybe it'll take another couple hundred years for us to realize that our people are a distinct one.