French, German, Portuguese and Italian are relative easy for another Indo-European to become fluent in, but they suffer from not especially useful to Americans.
In the case of French, I'd have to disagree with you. Africa is set to begin (or at least accelerate) its economic rise within the next few decades, and with a burgeoning population it would make sense for Americans to prioritize French (given it's the most widely spoken language on the continent besides English) in addition to Spanish.
You can include Algeria and Tunisia in the French zone, if you're there to do business it will be more useful than Arabic, beside the Mahgreb dialects tend to less than perfect intelligible with the Arab westerners usual learn (Classic or Egyptian).
...and I agree French is not a language in descline no matter what some people think.
But here's the problem, how often will a average American need French. There's a good chance for them to use Spanish, but French would rarely be useful for most Americans, and that's the primary purpose with the state using money to teach you a foreign language, it's a practical investment and French give little bang for the buck, through it's a better investment than Mandarin, Japanese or Hindi.
As such I believe it make sense for all Americans to learn Spanish as 1st foreign language, and let it be voluntary to learn more foreign language than the 1st. The ones who don't want to learn a 2nd, would likely neither learn it well or ever use it.