Department of Defense vs United States Department of Defense

Department of Defense and United States Department of Defense both are nouns.

Word	Noun	Adjective	Verb	Adverb
Department of Defense	Yes	No	No	No
United States Department of Defense	Yes	No	No	No

As nouns, Department of Defense and United States Department of Defense are synonyms defined as:

Department of Defense and United States Department of Defense: the federal department responsible for safeguarding national security of the United States; created in 1947

Other synonyms of Department of Defense include Defense, Defense Department, DoD.

Department of Defense (noun)	United States Department of Defense (noun)
the federal department responsible for safeguarding national security of the United States; created in 1947	the federal department responsible for safeguarding national security of the United States; created in 1947