American Civil War vs U.S.

American Civil War and U.S. both are nouns.

Word	Noun	Adjective	Verb	Adverb
American Civil War	Yes	No	No	No
U.S.	Yes	No	No	No

American Civil War (noun)	U.S. (noun)
civil war in the United States between the North and the South; 1861-1865	the executive and legislative and judicial branches of the federal government of the United States
	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