Is puerto rico part of the united states of america? if so how long has it been part of the usa?

on april 6, 1917, the u.s. joined its allies--britain, france, and russia--to fight in world war i. under the command of major general john j. pershing, more than 2 million u.s. soldiers fought on battlefields in france.

the western roman empire flourished, but the eastern portion of the empire struggled.