From the US Census Bureau website:

LANGUAGE SPOKEN AT HOME Population 5 years and over 254,746,174 English only 209,860,377 Language other than English 44,885,797 Speak English less than "very well" 19,492,832 Spanish 26,745,067 Speak English less than "very well" 12,463,516 Other Indo-European languages 9,479,670 Speak English less than "very well" 3,103,665 Asian and Pacific Islander languages 6,864,461 Speak English less than "very well" 3,395,653 Other languages 1,796,599 Speak English less than "very well" 529,998