U.S.A. vs middle west

U.S.A. and middle west both are nouns.

Word	Noun	Adjective	Verb	Adverb
U.S.A.	Yes	No	No	No
middle west	Yes	No	No	No

U.S.A. (noun)	middle west (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	the north central region of the United States (sometimes called the heartland or the breadbasket of America)