U.S.A. vs Philip Marlowe

U.S.A. and Philip Marlowe both are nouns.

Word	Noun	Adjective	Verb	Adverb
U.S.A.	Yes	No	No	No
Philip Marlowe	Yes	No	No	No

U.S.A. (noun)	Philip Marlowe (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	tough cynical detective (one of the early detective heroes in American fiction) created by Raymond Chandler