U.S. vs Keystone State

U.S. and Keystone State both are nouns.

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

U.S. (noun)	Keystone State (noun)
the executive and legislative and judicial branches of the federal government of the United States	a Mid-Atlantic state; one of the original 13 colonies, with capital Harrisburg
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