BFD! Not a single one of my ancestors set foot on North American soil before 1905--most of them came over in the 1920s. Guess I'm not an American, right?
Being an American--claiming to have allegiance to ANY nation, for that matter--has nothing to do with genetics. Nada, zip, zilch, zero. Ideals, baby. I am an American because I would fight for my country and I would die for my country. Being born here just means I can run for President.
I have to disagree with that statement. Some nations clearly have an ethnic aspect to their definition. You could live in Japan for generations and still not be considered Japanese, whereas Japanese immigrants to this country can become Americans as soon as they adopt this country's ideals.
You are confusing citizenship with nationality. Try using a dictionary to understand the definitions of words.