Originally Posted by Rosella
I must say I'm a bit mystified about the role of Puerto Rico, Guam, American Samoa and other overseas territories in the US political process. I do understand about them not being States, but why are their citizens allowed to vote in primaries, hold conventions and so forth but are not allowed to vote in the general election for President? It just seems a little odd.
Well, the primaries belong to the parties, so they can say (within constitutional limits) who participates and who doesn't. That's why some states have their Republican and Democratic primaries on different days, or even use different methods. The Commonwealth of Kentucky is a case in point - there's a Republican caucus on March 5th, and a Democratic primary on May 17th.
Both parties let the overseas territories participate in the nominating process. I think that's a fairly recent development, but I'm not sure. The overseas territiories can't vote in the actual election (that would require an actual amendment to the Constitution, like the 23rd which let the District of Columbia vote), but their inhabitants are American citizens*, and can vote if they become residents of the 50 states or DC.
It's kind of a mess, and has its historical roots in the fact that the Union was originally composed of sovereign states, but it seems to more or less work.
* Except American Samoa, as Shaggyrand points out.