USA vs Yank

USA and Yank both are nouns.

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

USA (noun)	Yank (noun)
the army of the United States of America; the agency that organizes and trains soldiers for land warfare	an American (especially to non-Americans)
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	an American who lives in the North (especially during the American Civil War)