U.S.A. vs in

U.S.A. and in both are nouns.

Word	Noun	Adjective	Verb	Adverb
U.S.A.	Yes	No	No	No
in	Yes	Yes	No	Yes

U.S.A. (noun)	in (noun)
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	a unit of length equal to one twelfth of a foot

U.S.A. (adverb)	in (adverb)
	to or toward the inside of