If the circumstances are as you described, your son is a natural born citizen and you should just ignore this stuff. Not that it’s particularly important unless he plans on being President.
I can’t imagine he would want to run for president. He is shy and likes to draw buildings. I don’t think there is anything that says he needs to be a definitive NBC to be an architect! :)
(BTW, since I have outed myself as a bad guy here, I want to thank you for all of the reasonable arguments you make in the face of frothing disdain. You are one of my favorites.) :)