Sargonarhes
I think most anime fans have also figured out Ohayo is 'Good morning' and hello is 'konnichwa' but when answering the phone you say 'moshi moshi'.
No we don't learn complete sentences, we're like Japanese children picking up a few words here and there. Any Japanese we'd try to speak would be broken because we don't know the full rules to speak the language, like we're all pre-schoolers.
When it comes to languages most other nations teach their kids english as a second language because it's the language of business world. For some reason in the US the only languages they offer in high school is french and spanish. Which doesn't really make much sense when it's been more important in recent years for business to know languages like arabic and chinese. Yes, the US has a very flawed education system.
Actually, the languages depend on the school. My high school offered French, Spanish, and Korean. They used to have German, but they discontinued it because of the lack of interest. Korean was offered because there was a large percentage of Koreans at my school, and Korean was the no. 1 most spoken foreign language at home in my city because again, of the large percentage of Koreans living in my city. Another high school in my district offered Chinese and Latin. And in Hawaii, Japanese and Chinese are taught in most schools.