USA vs federal department

USA and federal department both are nouns.

Word	Noun	Adjective	Verb	Adverb
USA	Yes	No	No	No
federal department	Yes	No	No	No

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