US Air Force vs United States Air Force

US Air Force and United States Air Force both are nouns.

Word	Noun	Adjective	Verb	Adverb
US Air Force	Yes	No	No	No
United States Air Force	Yes	No	No	No

As nouns, US Air Force and United States Air Force are synonyms defined as:

US Air Force and United States Air Force: the airforce of the United States of America; the agency that defends the United States through control and exploitation of air and space

Other synonyms of US Air Force include Air Force, U. S. Air Force, USAF.

US Air Force (noun)	United States Air Force (noun)
the airforce of the United States of America; the agency that defends the United States through control and exploitation of air and space	the airforce of the United States of America; the agency that defends the United States through control and exploitation of air and space