[Reaganwuzthebest]

They had in mind the following: members of American Indian Tribes, while on tribal land, provided the Tribe had status as an independent, sovereign nation; persons in the US under diplomatic immunity.

So prior to 1924 when Congress recognized American Indians as being included in the 14th Amendment what would have been the case if a woman who was a resident of a tribe went to a city hospital to give birth? Even though the hospital would have been within the boundaries of the US automatic citizenship was denied to her kid because she was not technically a citizen of the US. That's my understanding of how the law worked.

The same can be said of illegal aliens... they are not residents of this country and can be excluded unless Congress, as they did with American Indians chooses to include them.

[sourcery]

Any person physically on US territory is subject to US jurisdiction, unless that person has diplomatic immunity, or is an American Indian on his tribal land, where such land is recognized by treaty as the sovereign territory of the tribe. Persons who can rightfully argue in Federal court that the court has no authority over them are the only persons not "under the jurisdiction" of the US.