U.S.A. vs staffer

U.S.A. and staffer both are nouns.

Word	Noun	Adjective	Verb	Adverb
U.S.A.	Yes	No	No	No
staffer	Yes	No	No	No

U.S.A. (noun)	staffer (noun)
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	an employee who is a member of a staff of workers (especially a member of the staff that works for the President of the United States)