Actually, the Constitution requires that POTUS candidates must be natural-born citizens, which doesn’t necessarily mean they have to have been born in the US:
No person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President; neither shall any Person be eligible to that Office who shall not have attained to the Age of thirty-five Years, and been fourteen Years a Resident within the United States.
The 14th Amendment does say all people born in the US are automatically citizens, but you can also be a natural-born citizen if you were born abroad but at least one of your parents is/was a citizen at the time of your birth. That’s how, for instance, Ted Cruz was able to run for POTUS in 2016 even though he was born in Canada.