Nearly every American has two years of a foreign language in high school, and nearly every college requires two more years. I started Spanish in 7th grade and ended up with 5 years of study. However, I don't use is and as such, I've lost it.
I studied German for 4 years in school, and am far from fluent. I can painfully pick out details in a newspaper article, and can usually figure out if people are talking about soccer or food or whatever.
On the other hand, I'm fluent in French, and learned that in France, not in school.
In my experience, school wasn't a very efficient medium for learning languages.
The best (possibly only) way to learn a language on a functional level, is to use it. In my second-year Spanish class in high school, our teacher let us chat during class, so long as we chatted in Spanish and not English. In practice, we talked Spanglish, but nonetheless, that experience made me far better at Spanish than all my other studying before and after. She also taught all of her lessons entirely in Spanish, and required questions be asked in Spanish. While traditional lecturing is not an efficient medium for learning languages, schools can teach language skills very effectively by using alternative methods.
There are also Hawaiian Language Immersion schools available in Hawaii, which I hear very good things about.
There is an American actress - can't remember her name - she speaks fluent French. I saw her in a French movie and spent half the movie trying to place her face. It turns out that she went to a bilingual school French/English.
I teach German in a (Norwegian) high school, and I think your experience is typical. Most pupils forget everything they have learned as soon as they can after the exams, and only a very very few will go to Germany and make use of it.
And the Germans speak pretty decent English by now, so the payoff is not as great as it was.
If you're like most Americans, you never really had it. Were you fluent? I've "studied" it in school for 6 years (MS, HS, Univ), and I'm not even close to fluent. I don't think the school system is equipped to do that.
