The Constitutional requirement goes beyond that. A natural born citizen is a citizen without any doubt. Being born a citizen of another nation introduces doubt. How can Obama have been "naturally" born a citizen of the United States, when he was born a subject of, of all places, Great Britain, the very country our Founders sought to disentangle themselves from for all time?
The answer is, he wasn't. And, he admitted as much, on his own "Fight The Smears" website.
Such a site does not exist.