I don't think that there is only a problem of knowing other nations or cultures - for me there are more differences between social groups - social cultures within a country - Do you know them?! ...you are living a students live and you get to know other students, or living a soccer-player live and get to know other soccer-players - but are there really so many differences?! You are talking about foreigners but did you ever met and get to know people in your own country, who are "socially differnet"? Did you ever step out of your "Kaste", the "well-educated"? Aren't they kind of all the same just with differnent habbits, rules, experiences.. - natrurally because of another cultural backgound?
When I was in the Netherlands for Working out an European Report (we were 17 differnt european counrtries), we recognized one evening that we even have the same jokes in whole europe...-disappointing or not?