NBC was born of US citizens on US soil. It was so widely accepted that the term was used without definition in the constitution. Everyone knew it. That is, until obambam came along and turned us into an oligarchy over that issue.
We the people... secure the Blessings of Liberty to ourselves and our Posterity...
A natural born citizen is the Posterity of We the People, the citizen children of citizen parents.
The President was expected to be chosen from the Posterity of We the People in order to secure the Blessings of Liberty from being undermined by foreigners.
-PJ