BC would seem to be quite safe as the time it took for the rift to migrate to the west from the AB/BC border the crust was thickened quite a bit and the bedrock is quite stable until you get down to the Pacific NorthWest Scablands as the rift was under a thinner part of the crust..
By rights the Madrid fault should implode rather than explode and that huge new waterway would help being the moisture for the lake effect snow to the east and the 2km high ice while west of the river would be green until the desert started. I guess the silver lining is it is closer to Mexico and the ice market. The EU will have enough ice of it's own I would think. How much lake effect snow would the UK get if Buffalo was the small sacle model?