No he isn't.
https://en.wikipedia.org/wiki/Citizenship_Clause
“In Wong Kim Ark the Supreme Court held that, under the Fourteenth Amendment to the U.S. Constitution, a man born within the United States to foreigners (in that case, Chinese citizens) who have a permanent domicile and residence in the United States and are carrying on business in the United States[3] and who were not employed in a diplomatic or other official capacity by a foreign power, was a citizen of the United States”.
Using the above criteria.........
A woman illegally entering the United States to make it to the nearest hospital to have a baby DOES NOT MAKE THAT BABY A US CITIZEN.
Trump said today on O’Reilly he’s right about this and I believe him. He’s hired the best Constitutional lawyers in the world to prove it.