The fact that some can say s/he is American and some can also say s/he is Mexican cannot be said of a "Natural Born Citizen" of whatever nation you apply the NBC definition to.
Blood and soil, not one or the other, and in the olden days before one parent households became our norm, "blood" would have meant dear ol' dad.
It is what it is and it has always been so.
Your view has NEVER been true.
You are wrong.
I have already posted the Citizenship rules from the US State Department.