State Department vs US

State Department and US both are nouns.

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

State Department (noun)	US (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