All citizens of the territories and Puerto Rico have full US citizenship and vote in Presidential elections. Those citizens are free to move to the US mainland

All citizens of the territories and Puerto Rico have full US citizenship and vote in Presidential elections. Those citizens are free to move to the US mainland at anytime. In fact, living in US territories provides special tax advantages that are not available to US citizens in the mainland. There are historical and other reasons the territories aren't states -- Puerto Rico voters in particular have't supported statehood, and the other territories are very small and remote.