U.S. vs department of the federal government

U.S. and department of the federal government both are nouns.

Word	Noun	Adjective	Verb	Adverb
U.S.	Yes	No	No	No
department of the federal government	Yes	No	No	No

U.S. (noun)	department of the federal government (noun)
the executive and legislative and judicial branches of the federal government of the United States	a department of the federal government of the United States
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