From a formal (legal as well? IANAL) standpoint, Puerto Rico is an unincorporated US territory, and thus not a part of the United States. A territory has to be

From a formal (legal as well? IANAL) standpoint, Puerto Rico is an unincorporated US territory, and thus not a part of the United States. A territory has to be incorporated to gain that status. They're only considered part of the US for "specific legislation." https://en.wikipedia.org/wiki/Unincorporated_territories_of_the_United_States https://en.wikipedia.org/wiki/Unincorporated_territories_of_...