USA vs American

USA and American both are nouns.

Word	Noun	Adjective	Verb	Adverb
USA	Yes	No	No	No
American	Yes	Yes	No	No

USA (noun)	American (noun)
the army of the United States of America; the agency that organizes and trains soldiers for land warfare	the English language as used in 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	a native or inhabitant of the United States
	a native or inhabitant of a North American or Central American or South American country

USA (adjective)	American (adjective)
	of or relating to or characteristic of the continents and islands of the Americas
	of or relating to the United States of America or its people or language or culture