USA vs Northern United States

USA and Northern United States both are nouns.

Word	Noun	Adjective	Verb	Adverb
USA	Yes	No	No	No
Northern United States	Yes	No	No	No

USA (noun)	Northern United States (noun)
the army of the United States of America; the agency that organizes and trains soldiers for land warfare	the region of the United States lying to the north of the Mason-Dixon line
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