US Army vs bureau

US Army and bureau both are nouns.

Word	Noun	Adjective	Verb	Adverb
US Army	Yes	No	No	No
bureau	Yes	No	No	No

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

US 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 US Army include agency, authority, federal agency, government agency, office.

US 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