I added it late, but the real case to look at for Indians is Elk v Willkins...

The opinion in that case seems to be that Indian nations are sovereign and so an Indian born within an Indian nation is a citizen of that nation and not the US. This doesn't seem to be incompatible with the 14th Ammendment which mentions representation apportioned by whole persons, excluding Indians not taxed. US Citizenship of tribal members was also part of treaties between the US and the tribes.

That situation doesn't arise other than with Indians, because the US does not enter into treaties with any other groups formed within the boundaries of the US. Although the 1871 Indian Appropriation Act prohibited new treaties with Indian nations.