It places the inhabitants of the territory in political union with the people of the United States by providing American citizenship, and subsequently provides those citizens with the rights and responsibilities of that citizenship (primarily Federal representation and taxation) .
Why then, is Guam not a State of the Union? There are several factors which have prevented it in the past and will continue to prevent it from happening for an indefinite time to come.
There are the matters of distance and population. Guam is many thousands of miles away from its governing body, the U.S. Congress in Washington D.C. Not unlike the original thirteen British colonies in the early American continent did with England, Guam experiences much political frustration with U.S. arbitrary rule. Population is a severe issue when considering statehood for Guam. Whereas the mainland States and Hawaii all have populations in the millions, Guam has less than 150,000 people. Ecological studies of Guam have even shown that the island's water table will not be able to sustain more than 250,000 people. Many would argue that such a small population does not deserve equal representation with the larger States. The political tides and philosophies would have to turn significantly in Guam's favor before the rest of the nation entertains the notion of statehood for Guam.
A more pressing issue is one of Constitutional philosophy and legality. As mentioned before, there were people inhabiting Guam prior to the U.S. acquisition of it. Their history is an old and common one; that of a people being colonized by external empires. Guam has been colonized by three empires starting in the 1500's with Spain, Japanese occupation during World War Two, and now the United States.
It stands to reason that any colonized people (in this case, the Chamorros) would desire to maintain a sense of self, and identity. And as is usually the case with colonized peoples (for instance; Italy, Ireland, the Philippines, etc.
