What matters is the parents. They can be on official US government business or they can be tourists. If the parents are Americans, so is the brat, and from birth, making him Natural Born.
Of course, the kid's NBC status comes from being a citizen by reason of birth, as opposed to immigration / naturalization. That has the inconvenient side effect of also including Zero, should he not be shown to have been born abroad to unqualified parents (not going to happen, Abercrombie notwithstanding).
Of course, some of the nuttier birthers are on the same side as Janet Napolitano when it comes to the military. They'd like to exclude from the highest office military brats born abroad.
Natural Born Citizen is an eligibility requirement to be President of the United States per the Constitution.
It is not now, nor has it ever been, a type of citizenship.
Three types of citizenship are recognized by our government: native born (born in the U.S.); citizen by statue (born outside U.S. with one or more parents a U.S.citizen); and naturalized citizen (foreign national naturalized as U.S.citizen).
The only place in our legal system where Natural Born Citizen appears is as an eligibility requirement in the U.S. Constitution for President of the United States. NBC is NOT a type of citizenship but an eligibility requirement only and no one has a right to be President.
Natural Born Citizen is mentioned in SCOTUS cases and has been described thus: a Natural Born Citizen is born in the U.S.A. to citizen parents (both parents are citizens).
This indicates that to be eligible for the Presidency one must be born within the United States and both parents are citizens.
Ronald Reagan was born in Illinois to parents who were both U.S. citizens. He was eligible to be President.
Native born citizen: Gov. Jindal was born in the U.S. but his parents were then citizens of India. He is not eligible for the Presidency.
Citizen by statute: Sen. John McCain was born in Panama to U.S. citizen parents. The Panama Canal Zone was leased by the U.S. Government for administrative purposes and was NEVER U.S. territory. He is not eligible for the Presidency.
(In order for Sen. McCain to be eligible, a change to the U.S.Constitution would be required. That is a lengthy process involving all the States.)
Naturalized citizen: Gov. Arnold Schwarznegger was an Austrian citizen who naturalized as an U.S. citizen. He is not eligible to be President.
I hope this clarifies things for you. People can be citizens but not automatically be eligible to be President.