I don’t see how your question applies to the question of birthright citizenship. That seems to imply that nobody born here is a citizen.
The argument is that children born here to foreigners aren't really "subject to the jurisdiction" of the US because they somehow owe allegiance to their parents' country and therefore are not necessarily afforded citizenship under the 14th.
I think it's a silly argument and a lame attempt to get away from the plain meaning of the 14th as written.
Allegiance is something freely given, not passed along by birth, and unless you're a diplomatic agent of a foreign power, a member of a few selected Indian tribes, or a member of an occupying force you're subject to our jurisdiction.