Even canadian pilots cannot go sim training in the USA unless they accept to go through a very thorough security check by the US.
That isn't just IN the USA. If you want to do valid training related to an FAA license (for instance I hold an FAA ATPL and do recurrent every 6 months) you must submit to this Dept. of Justice check before training can be done. They (the D.O.J.)have even usurped the FAR's and pushed through a rule that if the training is done without DOJ approval, the training is invalid and must be repeated.
By the way, a request for this approval must be resubmitted EVERY time training is done. So in 6mos I submit to it again.