department of the federal government vs USA

department of the federal government and USA both are nouns.

Word	Noun	Adjective	Verb	Adverb
department of the federal government	Yes	No	No	No
USA	Yes	No	No	No

department of the federal government (noun)	USA (noun)
a department of the federal government of the United States	the army of the United States of America; the agency that organizes and trains soldiers for land warfare
	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