United States Army vs bureau

United States Army and bureau both are nouns.

Word	Noun	Adjective	Verb	Adverb
United States Army	Yes	No	No	No
bureau	Yes	No	No	No

As nouns, bureau is a hypernym of United States Army; that is, bureau is a word with a broader meaning than United States Army:

United States Army: the army of the United States of America; the agency that organizes and trains soldiers for land warfare
bureau: an administrative unit of government

Other hypernyms of United States Army include agency, authority, federal agency, government agency, office.

United States Army (noun)	bureau (noun)
the army of the United States of America; the agency that organizes and trains soldiers for land warfare	furniture with drawers for keeping clothes
	an administrative unit of government