Although many of them are only represented by relatively small populations, the US has a much wider range of languages and language groups than Europe, as it has the languages brought from Europe, the creole languages from the slave trade, as well as the remaining native languages.
That's the relevant part for the purpose of calling it a single market.
>the US has a much wider range of languages and language groups than Europe
Unless you're talking about Indigenous languages with less than 10k speakers, that's not true because Europe has experienced significant immigration over the past decades.
If you are talking about those languages, it's irrelevant because fewer than 150k people speak them, and only a few thousand aren't also fluent in English.
