It's important to learn a foreign language if you plan on traveling outside the U.S., and there are many cities in North America where knowing French, Spanish or Chinese will help you feel at home.
It's equally important to learn another language or three if you want to catch all the non-English jokes hidden in your favorite movies.
Then you would know Christian Slater's character J.D. was lying when he said he had "Ich Luge" (I'm lying) bullets in Heathers, and you would have noticed Bruce Wayne is driving a Lamborghini Murciélago in The Dark Knight, which is Spanish for "bat". (NSFW due to language)
I will never think of the expression "ho there" the same way ever again!