Just to be clear on what you think, are you saying that if one's parent is from another country, even if that parent becomes an American citizen before the child is born, the child cannot be an NBC?
Maybe you just got caught up in brevity? Once the parent becomes an American citizen, their place of birth is no longer relevant when conferring natural born citizenship on their children. It's only when one parent has not yet become an American citizen that the child fails the NBC test.
-PJ
It depends on which Birther you ask.
Some are of the ‘Father needs to be a citizen, but not the mother’ sect and others are of the ‘two parent’ sect.