The LCME has accredited all Canadian medical schools meaning Canadian graduates don't need to complete residencies in the US to practice. They don't have to sit the exams either in the 40 states that consider the Canadian LMCC to be equivalent to FLEX. So "all" they need is a H-1B visa bearing in mind that the Federal regs *don't* regard LMCC as equivalent to FLEX. ;-) . Other physicians may receive special treatment in this respect if they are regarded as extraordinary or of special importance to the country, though these circumstances aren't widely publicized for obvious reasons.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
