Help Me Choose a Language to Learn.

I live in the United States. I am fluent in English. I know nothing of any other language. I would love to know what the most useful language will be in the future. I'm going to be dual-enrolling soon at a local university, and I wanted to take a class which is unavailable to me.

Can you suggest a language? The only classes currently available to me through my high-school are Spanish and Latin.

>>French

No. Only in French Canada, but they speak English too.