Well known fact - this is one of the biggest pop/country crossover hits in history. It's pretty easy to see why - it's a catchy song with lyrics that work even forty years after its initial success.
Country music is largely an American phenomenon. Outside of the States, it usually doesn't play as well, but here, it is the most popular genre. This song is one of the exceptions to the rule. Here is Anderson performing the song in 2009, in Norway. It looks like the Norwegians are enjoying it, even if they had trouble saying "Howdy"!