If Trump imposes a 20% import tax on Canadian imports won't that tax just be passed on to US customers?
And won't it just create countervailing duties on US exports to the USA .. because that's how a trade war happens?

Also, could Canada impose a tax on all energy being exported to the USA... oil, gas and the big one ELECTRICITY to the US Eastern seaboard states?  Shut off the electricity and Eastern USA goes dark!!

Also, could Canada charge a tax on Alaska oil being transported across Canada into the USA?

Somehow I suspect POTUS Trump will give Canada a "most-favoured" nation status.... because Canada is intrinsic to the North American partnership and history.  i.e. we have the same GDP as California... iow, we are California North ...{{{brrrr}}}

Trump: "I love Canada... they're fantastic... fabulous.... greeeaaaat ... and I love Justin and want a selfie with him.... and so does Melania and Ivanka!!!"