??? Her being underage is critical. If she had been a US resident for 5 years after her 14th birthday, and had lived a total of 5 more years in the US (she had, actually she had lived 14 more years), then it would not matter where she gave birth. But she did not live in the US for 5 years after her 14th birthday. So if BHO Jr. was born outside the US, he'd ineligible, an open and shut case. However if he was born in the US, then things are little more complicated, due to his father being a foreign national, and the possibility of his having conflicting loyalties. However IMHO that doesn't matter, and if he was born in the US he is a natural born citizen.
I think you have this figured out.
Which is why our focus is on keeping the burden of proof on Obama to produce the real birth certificate.
El Gato, I think your last line is the crux of the situation. IMHO, BHO was indeed born on US soil, and if that is the case, then he is a natural born citizen.