I think we have some strange ideas about how and why studying languages are "useful". Most Americans are monolingual English speakers, and almost by definition can't study a language that's more "useful" than English.

There are large cognitive benefits to bi- and multilingualism, but for these it doesn't actually matter what language you speak: a heritage or minority language is as good as anything else.

But the classroom model of the United States isn't actually designed to make people multilingual; if anything, it's the opposite. The default language policy of the United States is mostly to shift people to English monolingualism, no matter their circumstances, heritage, or language rights.