Currency markets act a bit like electomagnetic law (Lenz's law) where any change is opposed by a magnetic field response that opposes the original change.  

If all this ever comes to pass, which I doubt, then almost instantly the CAD-USD exchange rate will adjust to compensate; a 65c dollar would be about right for the proposed US corporate tax rate of 15%.

On top of that, Canada could respond by eliminating all corporate tax period.  Thats right, take it to ZERO.  This is WAR.