You should be concerned anyhow if a major eruption were to occur from either Yellowstone or Mt. Rainier, energy and ash output scaled up appropriately from Mt. St. Helens. Say goodbye to wheat production, barley, dry edible beans, sugar beets, canola, flax, lentils, oats, potatoes, corn, apples, etc., etc., transportation, Seattle and Vancouver ports, power for midwest factories, melting Great Lakes ice cover in the summer and on and on.
Vancouver BC is not likely to be much affected, nor is any other west coast port.