harvest mouse vs American harvest mouse

harvest mouse and American harvest mouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
harvest mouse	Yes	No	No	No
American harvest mouse	Yes	No	No	No

As nouns, harvest mouse and American harvest mouse are synonyms defined as:

harvest mouse and American harvest mouse: any of several small greyish New World mice inhabiting e.g. grain fields

harvest mouse (noun)	American harvest mouse (noun)
small reddish-brown Eurasian mouse inhabiting e.g. cornfields	any of several small greyish New World mice inhabiting e.g. grain fields
any of several small greyish New World mice inhabiting e.g. grain fields