Wikipedia tells us

According to the 2000 census,[9] the main languages by number of speakers older than five are:

1. English - 215 million
2. Spanish - 28 million
3. American Sign Language - 2.0 million
4. Chinese languages - 2.0 million + (mostly Cantonese speakers, with a growing group of Mandarin speakers)
5. French - 1.6 million
6. German - 1.4 million (High German) + German dialects like Hutterite German, Texas German, Pennsylvania German, Plautdietsch
7. Tagalog - 1.2 million + (Most Filipinos may also know other Philippine languages, e.g. Ilokano, Pangasinan, Bikol languages, and Visayan languages)
8. Vietnamese - 1.01 million
9. Italian - 1.01 million
10. Korean - 890,000
11. Russian - 710,000
12. Polish - 670,000
13. Arabic - 610,000
14. Portuguese - 560,000
15. Japanese - 480,000
16. French Creole - 450,000 (mostly Louisiana Creole French - 334,500)
17. Greek - 370,000
18. Hindi - 320,000
19. Persian - 310,000
20. Urdu - 260,000
21. Gujarati - 240,000
22. Armenian - 200,000

Are American signers to be regarded as unAmerican because they don't speak English?

Why stop there? Why not insist on Anglo-Saxon. After all, look at Iceland. That's pretty much a "pure" country (mostly Scandinavian stock, but a bit of Irish blood, too) speaking a language that hasn't changed very much for over ten centuries.

Although the USA does not have "official" languages, it has a number of States which are unofficially bi-lingual, and one state which is officially bi-lingual. Four Territories are also officially bi- or tri-lingual, but they don't count - they're only colonies, not proper Americans.