The article isn't focused on students but I still think this covers some of the possible reason's it isn't as common in the U.S. (of course this is just a broad generalization) -
http://www.cnn.com/2011/TRAVEL/02/04/americans.travel.domestically/I would add that I think a second/third/etc language through school is more common outside of the U.S..
FWIW I personally know quite a few Canadians who did something along those lines (although admittedly some of the families I'm thinking of weren't necessarily looking for deceleration due to gifted issues - they just wanted their kids to experience travelling).
Many of the most ambitious Canadians will wind up in the U.S., and if I were a Canadian parent, I might want my children to spend some time in the U.S. To be successful, it's not as important for Americans as it is for people from many other countries to travel abroad or to learn a second language. My eldest son is starting to take French this year, and I want him to do well. But for me a foreign language has just been a hoop to jump though to get into a good college, and it may well be the same for him. His learning of computer languages will probably be more valuable to him.
