Residents of US territories are able to receive birthright citizenship if an act of Congress grants it to them. While Congress's refusal to do so for residents of American Samoa has clear racist roots, the Court declined to hear a case challenging this exclusion.
SOURCE: The New Republic
Unique among non-state U.S. territories, people born in American Samoa are not granted citizenship by birth. This legal anomaly traces back to the acquisition of Pacific islands from Spain in a climate of American imperialism and white supremacy.