US law considers him a citizen of the US. Whether other countries also choose to consider him a citizen is irrelevant.
There are only two categories of citizen: natural born and naturalized. There is no "neither of the above" category.
He is a citizen, and he did not have to be naturalized. Therefore he is a natural-born US citizen.
You Are Totally Correct. See #19
Better read the qualifications again.Not only does he have to be a natural born citizen,his parents have to be citizens of the U.S.