A lot of Americans speak more than one language, but it's not necessary here. I speak some Spanish and I don't think it's ever a bad thing to have more knowledge. But it takes time to learn a new language, time that could otherwise be spent working or doing more productive things that will directly affect the quality of our lives here.
Simply put, we don't need it...that doesn't make us uncultured or dumb.
We have our own culture and part of that culture is the English language. It's also a language that originated in Europe.
Yes, you can use those languages for business or when on vacation, and like I said, that's not a bad thing. Just not a necessity.