You are confused. Marco Rubio was born in Miami, USA, his parents were Cuban, who escaped the barbarism of Fidel Castro. (The people only trotted out when needed, those who have been true conservative loyalists) The ineligible candidate would have been Ted Cruz.
Natural born citizen means born here of citizen parents.
No possibilty of being anything else. Solely an American.
Children of foreign nationals are not natural born citizens.
They acquire the nationality of their parents even if they are afforded (incorrectly) US citizenship.
No foreign birth
No foreign parent(s)
No foreign citizenship(s)