I worked with a French guy in Amsterdam. His parents were Portuguese, but he was born and raised in France. As far as he was concerned, he was French.

Contrariwise, I worked with an American woman in Virginia. Her grandparents were Irish, and she considered herself Irish, in spite of having been born and raised in America, and both of her parents having been born and raised in America.

It is a kind of fetish in America to hyphenate yourself. Irish-American. Cuban-American. And so on.

My own theory is that this is because America has no culture going back many generations, so people try to find one.