The USA comprises 50 states. Fifty states compose the USA.Careful writers will maintain this distinction. But, increasingly, the usage panels of major dictionaries are accepting the use of comprise for compose, especially in the passive voice. Thus:
Fifty states constitute the USA.
Fifty states make up the USA.
The USA is comprised of 50 states.According to Bryan Garner, however, the expression is comprised of is “always wrong and should be replaced by some other, more accurate phrase….” Garner, Oxford, p. 75.