white elm vs American elm

white elm and American elm both are nouns.

Word	Noun	Adjective	Verb	Adverb
white elm	Yes	No	No	No
American elm	Yes	No	No	No

As nouns, white elm and American elm are synonyms defined as:

white elm and American elm: large ornamental tree with graceful gradually spreading branches common in eastern North America

Other synonyms of white elm include rock elm, Ulmus americana, water elm.

white elm (noun)	American elm (noun)
large ornamental tree with graceful gradually spreading branches common in eastern North America	large ornamental tree with graceful gradually spreading branches common in eastern North America