Oh no it's very hard. You go to NYC and spend weeks in barber shops and ethnic restaurants until you hear the fragments of the nearly extinct tongue. Name the language and it is likely spoken in the five boroughs.
A buddy from Latin America who barely spoke English moves to the US. Specifically, he moves to Bushwick, Brooklyn, NYC. He goes, "They all say, 'You gotta learn English. This is America!' but I can't understand any of them - even the Puerto Ricans." First thought in my head was 'dude, you're learning English on hard mode'.
Ranking individual things as more or less diverse than other things is a gross abuse of the concept of diversity anyway. But yeah cataloging the set languages spoken in the US is likely impossible in any meaningful way.
