@Eran: It's a trendy thing to put American. Means you don't recognize your old ancestry; you only recognize being part of America. Or something like that.
Well, I consider myself American, not Irish-American or German-American or English-American or whatever; I still know what my ethnicity is. I thought that might be it, it's the same as "No Data" because too many people don't want to give a straight answer.