Ethnologue, Languages of the WorldThe number of languages listed for USA is 231. Of those, 176 are living languages, 3 are second languages without mother tongue speakers, and 52 are extinct.
From Afro-Asiatic to Zaparoan, the Ethnologue can show where and how many people speak each language in the world.
Full of language info, maps and history. Searchable on line.
Ethnologue, Languages of the World