State Department vs United States of America

State Department and United States of America both are nouns.

Word	Noun	Adjective	Verb	Adverb
State Department	Yes	No	No	No
United States of America	Yes	No	No	No

State Department (noun)	United States of America (noun)
the federal department in the United States that sets and maintains foreign policies	North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776
a department of government in one of the 50 states