If you want to read a weird mix of Trump and Sanders supporters agreeing here it is (plus a hilarious misunderstanding of how free trade works).
So if your parent(s) are American and you're born in some country while your mom is travelling, are you not a natural born citizen? What if one parent is and you're born on a military base? What about a US territory?
I'm no lawyer, but if you're born a citizen, to me that is natural born. To be born a citizen, you're either born to at least one parent who has US citizenship or you're born on US soil.