NPC vs government agency

NPC and government agency both are nouns.

Word	Noun	Adjective	Verb	Adverb
NPC	Yes	No	No	No
government agency	Yes	No	No	No

As nouns, government agency is a hypernym of NPC; that is, government agency is a word with a broader meaning than NPC:

NPC: an agency that serves as the focal point for all Intelligence Community activities related to nonproliferation of weapons of mass destruction and their missile delivery systems
government agency: an administrative unit of government

Other hypernyms of NPC include agency, authority, bureau, federal agency, office.

NPC (noun)	government agency (noun)
an agency that serves as the focal point for all Intelligence Community activities related to nonproliferation of weapons of mass destruction and their missile delivery systems	an administrative unit of government