American English vs backward

American English is a noun but backward is not a noun.

Word	Noun	Adjective	Verb	Adverb
American English	Yes	No	No	No
backward	No	Yes	No	Yes

American English (noun)	backward (noun)
the English language as used in the United States

American English (adjective)	backward (adjective)
	directed or facing toward the back or rear
	(used of temperament or behavior) marked by a retiring nature
	retarded in intellectual development
	having made less than normal progress

American English (adverb)	backward (adverb)
	in a manner or order or direction the reverse of normal
	in or to or toward a past time
	at or to or toward the back or rear