I need to give this more thought, but I believe a tit-for-tat strategy (and variant's on tit-for-tat) apply mostly to zero-sum games (any win for me is an equivalent loss for my opponent).  I am not certain you can describe something as complex as trade between Canada and the US as a zero-sum game.  I am also not certain you can describe the politics involved between or within each country as zero-sum either so I am not at all certain tit-for-tat is the right way forward.  Retaliation (reciprocity really) always feels good and has the advantage of simplicity and predictability.  It might not be the smart move.