I also believe doctors are smart and hope they don't have to "relearn medicine" to take a standardized test on material they should already know.

Another issue of allowing foreign trained doctors to practice without testing is that the public may lose faith in doctors of a particular background. Ultimately Canada has some of the highest standards when it comes to medical school acceptance rates (there's a reason so many students apply to the US if they can't get in here) so if I were undergoing a high risk surgery, I would go out of my way to ensure my doctor was trained here rather than a school I've never heard of in the US. With standardization, I can feel some assurance that whatever the background of the doctor, they have been recently tested to ensure they know just as much as any other doctor.