eastern United States vs East

eastern United States and East both are nouns.

Word	Noun	Adjective	Verb	Adverb
eastern United States	Yes	No	No	No
East	Yes	No	No	No

As nouns, eastern United States and East are synonyms defined as:

eastern United States and East: the region of the United States lying to the north of the Ohio River and to the east of the Mississippi River

eastern United States (noun)	East (noun)
the region of the United States lying to the north of the Ohio River and to the east of the Mississippi River	the countries of Asia
	the region of the United States lying to the north of the Ohio River and to the east of the Mississippi River