Based on my recent correspondence with the CTY-SET program, they are only accepting the SAT at the moment (the more general CTY program though, does accept a multitude of other tests)

More so than biasing towards US/mathy kids, the CTY-SET -- or any of these talent search programs in general -- seems to be biased towards families who have the resource to do the reasearch and jump through all the hoops to get their kids tested.