"All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside."
Doesn't really take a constitutional law expert to interpret one of the most straightforward sentences in the Constitution.
Trump is full of shit on this one, and he's gonna lose -- but I'm sure he knows he's gonna lose. And this is the thing that people continually get wrong about Trump. The outrageous thing he says he wants -- well, if he can get it, great, but it's always always always the starting point of the negotiation, and it's always provocative so it's easier for him to get what he actually wants.
China, Russia: you want a world where everyone takes what they want? Fine, we'll take Panama and Greenland.