USA vs billionth

USA and billionth both are nouns.

Word	Noun	Adjective	Verb	Adverb
USA	Yes	No	No	No
billionth	Yes	Yes	No	No

USA (noun)	billionth (noun)
the army of the United States of America; the agency that organizes and trains soldiers for land warfare	one part in a billion equal parts
North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776	position 1,000,000,000 in a countable series of things

USA (adjective)	billionth (adjective)
	the ordinal number of one billion in counting order