Geography matters, but so do governments. If you live in a place that flies the American flag, should you be entitled to all of the privileges that are shared by all the residents of lands where that flag is flown?
No, says the Court of Appeals for the District of Columbia. Citizenship belongs to those persons whose populace and locally elected government opt to incorporate as a territory or be accepted as a state.
The American Samoa people and government have not opted for that aspect of governance and therefore its residents, though "nationals" of the United States are not "citizens" of the United States.
The case is Tuaua v. United States of America and the opinion can be found here.
In Tuaua, a resident of American Samoa challenged his status as a national of the United States under the Citizenship Clause of the Fourteenth Amendment. That clause provides:
“[a]ll persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.”
So, if the resident of American Samoa is "in" the United States, it follows that he should be a citizen of the United States.
Not so, says the court. Hearkening back to, and ultimately being bound by, the Insular Cases, citizenship is reserved to those persons whose neighbors and governments have opted to incorporate their territory into the national franchise. Short of that, the courts are not going to force the benefits, and obligations, of citizenship on a people.
I posted on Hawaii's history of statehood following the Insular Cases here.