There are so many ways in which information gets shared. Misinformation, too. Stereotypes get reinforced, unrealistic hopes built (and dashed), and people see the best, and worst, of each other. Television and movies are prime culprits in this regard, aren't they?
If you believe the movies and tv shows, all Germans are neat, organized and blue-eyed/blond-haired. The French won't speak to Americans because we don't speak French. Italian men are Lotharios. All Brits have bad teeth. You can't drink the water anywhere outside the US, orphans and whores have hearts of gold, and a twisty road is sure to have a car chase erupt regularly.
It's more than just culture, it's professions. Teachers care about even the most troubled students. Nurses (when not trying to sleep with doctors) have endless patience. If you believe Law & Order, cases are easily solved and rarely do the bad guys win. Local new stations resemble WJN. Teen girls dress and talk older than they should, while their mother's look as though they were giving birth at the onset of puberty.
And then there's House. If you believe the show, every trip into an MRI ends up with the patient bleeding uncontrollably... convulsing... going blind... having interior metal ripped out through their skin... going into V-tach...
Not the most comforting thoughts to have as you lie in an MRI machine for an hour.