USA vs State Department

USA and State Department both are nouns.

Word	Noun	Adjective	Verb	Adverb
USA	Yes	No	No	No
State Department	Yes	No	No	No

USA (noun)	State Department (noun)
the army of the United States of America; the agency that organizes and trains soldiers for land warfare	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