Lessee, how did he get there?
Actually speaking, since the PI was a US territory when he was born, he does fit the "natural born citizen" clause.
Never thought of that, what happens if the place where you were born is no longer part of the US? Do you lose your citizenship, or do you retain it?
But, it get's kind of bad.
Now, if the PI referendum changes and they elect to become a US state instead of an independent nation...well, that makes this a lot more plausible.
Maybe this is a world where the WWII lasts longer, but the PI holds out and manages to standoff the Japanese.
Maybe this is a world where the Japanese decided to sit it out, and never bombed Pearl, managed to get the oil concessions somehow without going to war, but a Cold War is going on between Japan and the Pacific Allies, and PI is an American State, and highly important to US policy.