I have a Canadian friend who feels the same way. America is a HUGE kemrat place, but no matter how talented the artist, the kemrat is quite fickle. If you are selling now, that may not be the case in 2 years, so it behooves an artist to make the best of their 15 minutes. It's not the artists driving this fickle kemrat, it's the media and the money people. (They will refer to 10 year old song as classic! We have developed an appetite for new and cutting edge that is unsustainable, it's a pity really.) Another reason people like to work in America our tax laws are like Swiss cheese which means that they can keep more of their cheese if you know what I mean. As for whether or not they return to their home countries after the party is over, I guess that just case by case.