OK, so without the grandfather clause, no one was eligible because the United States didn’t exist prior to ratification, so no one could have been a “natural born citizen” of the United States. Agreed.
The point is, that would have been true, regardless of whether “natural born citizen” depends on birthplace, parentage, or both. If birthplace determines “natural born citizen” status, then no one could have been a “natural born citizen,” because no one had been born in the United States 35+ years prior. If parentage determines “natural born citiszen” status, then no one could have been a “natural born citizen,” because no one could have been born to United States citizen parents 35+ years prior. So, trying to argue that the existence of a grandfather clause proves that “natural born citizen” status depends on parentage is incorrect.
That wasn’t the context of the conversation.
Natural Born Citizenship is determined by a combination of three things, all of which have to be the same. Mother’s citizenship, Father’s Citizenship, and Place of birth.
All must be of the same nation in order to be a Natural Born Citizen of that Nation. This person was born under the sole jurisdiction of ONE nation, and has zero possibility of any other citizenship.
You cannot logically state that the Citizenship of Mom goes away, certainly not today, nor that of Dad. The citizenship of a parent doesn’t just disappear. The place someone was born, if on foreign soil may or may not confer automatic citizenship, but certainly creates the likelihood of dual citizenship. No one argues that an anchor baby doesn’t inherit his Mexican parents citizenship! He is Mexican and American.
So place matters, Parents matter, and in Natural Born Citizenship all three matter.