Keystone State vs U.S.

Keystone State and U.S. both are nouns.

Word	Noun	Adjective	Verb	Adverb
Keystone State	Yes	No	No	No
U.S.	Yes	No	No	No

Keystone State (noun)	U.S. (noun)
a Mid-Atlantic state; one of the original 13 colonies, with capital Harrisburg	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