There is nothing secretive or complex about jurisdiction when the issue is "in personam" jurisdiction for purposes of constitutional application. If a living human being is within the borders of the US, including any territory or possession, that person is subject to the jurisdiction of the American law and the judiciary for all purposes. The attempt to create some fatuous distinction and non-extant ambiguity is meaningless. The question is so finally resolved that it wouldn't even make a good constitutional law I exam question.
If that is so absolutely unerringly obviously true, then why did it take until 1924 for an act of Congress to make Native Americans citizens of the United States? As you state it, Native Americans would have been considered citizens by virtue of the fact that they were born "within the borders of the US, including any territory or possession" but they were not. If Congress can declare that Native Americans are or are not citizens, then Congress can declare illegal aliens to be citizens or not by dint of legislative fiat, just as they did for Native Americans can they not? If they cannot, what's the Constitutional difference under the 14th Amendment between a Native American non-citizen in 1918 born in Oklahoma prior to the enactment of the Indian Citizenship Act of 1924 (who would not have been considered a citizen) and an illegal Mexican alien born in also born in Oklahoma in the same time period?