It doesn’t matter whether his father was a citizen. If you are born in the US you are a natural born citizen, no matter who your parents are.
That is just soooooooo wrong.
Actually the relevant text on NBC the law of nations, would differ with your take, as would the founding Fathers. The founders were worried about allegiance, thus the NBC wording in the constitution. They would have stated that any one with a father who was not a citizen at the time of their birth would not be an NBC, a citizen possibly but not a NBC.
At the time of the writing of the constitution citizenship flowed from the father. Location had no control on the issue. In fact there are only 14 countries that allow birthright citizenship, and all but the USA need to increase their population.
And as to the 14th amendment, it has not been applied as intended, and the authors would have told you that being here illegally and squirting out a child would not have conferred citizenship on that child. The specific reason for the 14th amendment was to force the democrats to recognize slaves as citizens.