After four centuries of Spanish rule, Puerto Rico was ceded to the United States in 1898. Residents were granted U.S. citizenship in 1917, and the federal government has allowed Puerto Rico to exercise authority over its local affairs in a manner similar to the 50 states.
A territory cannot become a state or a nation unless Congress approves legislation and the president signs it.
The government of Puerto Rico has every right to hold a plebiscite, to consult the people of Puerto Rico regarding their wishes. But the truth is that for a change in the status of Puerto Rico to happen, you need both Congress and Puerto Rico agreeing to it.