You can ask the seller to cancel the bid (or how much he would charge to ship to Canada using USPS First Class International Package, which gives him Confirmation of Delivery).
https://ircalc.usps.com/
Or, you can retract your Bid.
http://pages.ebay.ca/help/buy/bidding-overview.html
There are not many reasons for retractions. Pick one that seems vaguely reasonable.