US Coast Guard vs United States Coast Guard

US Coast Guard and United States Coast Guard both are nouns.

Word	Noun	Adjective	Verb	Adverb
US Coast Guard	Yes	No	No	No
United States Coast Guard	Yes	No	No	No

As nouns, US Coast Guard and United States Coast Guard are synonyms defined as:

US Coast Guard and United States Coast Guard: an agency of the Department of Transportation responsible for patrolling shores and facilitating nautical commerce

Other synonyms of US Coast Guard include U. S. Coast Guard.

US Coast Guard (noun)	United States Coast Guard (noun)
an agency of the Department of Transportation responsible for patrolling shores and facilitating nautical commerce	an agency of the Department of Transportation responsible for patrolling shores and facilitating nautical commerce