USA vs Philip Marlowe

USA and Philip Marlowe both are nouns.

Word	Noun	Adjective	Verb	Adverb
USA	Yes	No	No	No
Philip Marlowe	Yes	No	No	No

USA (noun)	Philip Marlowe (noun)
the army of the United States of America; the agency that organizes and trains soldiers for land warfare	tough cynical detective (one of the early detective heroes in American fiction) created by Raymond Chandler
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