I read a very interesting article the other day* on one man's theory why British people (and let's expand this to pretty well most native English speakers) don't speak foreign languages well, if at all.
The basic reason, he suggested, was nothing to do with our ability to learn languages but more to do with what languages to learn.
Take a typical Russian. Or Belgian. Or Peruvian. If they want to learn a foreign language then there's really only one choice: English.
With English under their belt they can set off around the world and order food and survive in every city from Acapulco to... whichever city begins with Z.
But pity the poor old English speaker. What language should they learn? If they learn German then... well they can get by in Germany and that's pretty much it. Spanish might be better because then they can get by in Argentina and Colombia... but if they cross the border into Brazil it might get a little tricky.
The most spoken language in the world is Mandarin so if our English speakers all learn that they can get by fine in China and Hong Kong and... not many other places.
But if they don't bother to learn another language they can go out with their mother tongue and get by in pretty well every place on earth so really it all boils down to English being too successful as a world language.
And that's why English native speakers so rarely speak other languages!
* Slaves to the Network by Rory Sutherland published in The Spectator, June 23rd, 2012.