staff member vs USA

staff member and USA both are nouns.

Word	Noun	Adjective	Verb	Adverb
staff member	Yes	No	No	No
USA	Yes	No	No	No

staff member (noun)	USA (noun)
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)	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