eastern United States vs U.S.A.

eastern United States and U.S.A. both are nouns.

Word	Noun	Adjective	Verb	Adverb
eastern United States	Yes	No	No	No
U.S.A.	Yes	No	No	No

eastern United States (noun)	U.S.A. (noun)
the region of the United States lying to the north of the Ohio River and to the east of the Mississippi River	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