Niagara River vs U.S.A.

Niagara River and U.S.A. both are nouns.

Word	Noun	Adjective	Verb	Adverb
Niagara River	Yes	No	No	No
U.S.A.	Yes	No	No	No

Niagara River (noun)	U.S.A. (noun)
a river flowing from Lake Erie into Lake Ontario; forms boundary between Ontario and New York	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