USA vs Midwest

USA and Midwest both are nouns.

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

USA (noun)	Midwest (noun)
the army of the United States of America; the agency that organizes and trains soldiers for land warfare	the north central region of the United States (sometimes called the heartland or the breadbasket of America)
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