[sourcery]

"Subject to jurisdiction" means more than than just physical presence on the soil, it entails sworn allegiance to the country as well as being a citizen.

Your definition is circular. Your statement reduces to "you're a citizen if you've agreed to be a citizen."

The 14th Ammendment is does not establish a protocol for determining, moment by moment, whether or not someone is a citizen. One does not become a citizen by virtue of coming under US jurisdiction, and then lose citizenship upon exiting--perhaps several times in an afternoon, if one lives very near a national border. From the language, the context of the times, and the preceding logic, it is clear that the question of jurisdiction clearly was meant to be of import at precisely one moment, and only at that moment: the moment of birth.

And the meaning of jurisdiction is also perfectly clear. It's dictionary definition:

1. Law. The right and power to interpret and apply the law: courts having jurisdiction in this district.
   • Authority or control: islands under U.S. jurisdiction; a bureau with jurisdiction over Native American affairs.
   • The extent of authority or control: a family matter beyond the school's jurisdiction.
2. The territorial range of authority or control.

[Reaganwuzthebest]

Even accepting your definition of "subject to jurisdiction" at its face value without the sworn allegiance and citizenship requirements how do you explain the fact that prior to 1924 American tribal Indians could give birth in a public hospital and their kid be denied automatic citizenship? You haven't answered me on that.

The Supreme Court ruled in 1884 against an American Indian named John Elk, who despite being born in Nebraska territory and outside his tribe was not considered a citizen.

The majority opinion of the Court read:

The evident meaning of [the jurisdiction phrase] is not merely subject in some respect or degree to the jurisdiction of the United States, but completely subject to their political jurisdiction, and owing them direct and immediate allegiance. Indians born within the territorial limits of the United States … although in a geographical sense born in the United States, are no more ‘born in the United States and subject to the jurisdiction thereof’ within the meaning of the [Citizenship Clause], than the children of subjects of any foreign government born within the domain of that government…

That Court's decision has never been overturned and explained why in 1924 Congress provided legislative relief to American Indians. The Court ruled btw children of illegal aliens are not citizens of this country.