In light of North Korea's threat to bomb Guam some people have asked me about US territories. There are 4 inhabited, organized territories: Guam, Northern Mariana Islands, Puerto Rico and the US Virgin Islands. All US Federal laws are the same as with the 50 States and DC and all are US citizens.
There is 1 inhabited, unorganized territory: American Samoa. Not all Federal laws (like gay marriage) are the same as the 50 States and DC and the people there are US nationals, but.not US citizens.
There are many uninhabited US territories around the world (mostly in the Pacific.) Uninhabited in this case can mean there are no ordinary civilians allowed, but only the military or government employees.
There are also 3 independent countries that form a Compact of Associated States with the US: Micronesia, Palau and the Marshall Islands. The citizens of each country can go to any of the 4 countries and live and work as though they are regular citizens. The US Federal Government also maintains: the US Post Office, Military, FEMA, FAA, Medicaid and FCC for those places.