East vs eastern United States

East and eastern United States both are nouns.

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

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

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

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