Its not a problem. Jokes about Canada being the 51st state aside, Canada is a different country. It is treated as the same country for purposes of an open jaw, so that you can start in Vancouver but end in New York, or vice versa. The only other place that it matters is that flying between CA and the US is not interntational travel. It says nothing about flying from the US to other countries. The rule exists primarily because of the seven day trip minimum. So when calculating the seven days, on a trip that went YVR-DFW-NRT-LHR-DFW-YVR, the clock would start ticking when you left Dallas, not when you leave Vancouver.