I don't know if it is true in the camera industry but in many other industries of which I have first hand knowledge, US retailers wholesale price is frequently 10-20% cheaper then Canadian wholesale. This is usually directly related to Canadian distribution. The manufacturer restrictions are put in place to protect the Canadian retailer who just can't compete. Some larger ones volume discounts/buying groups may put them in a position to compete but definately the smaller retailer cannot. What really needs to happen in many industries is the wholesale pricing needs to be the same in both Countries and there really isnt a reason that it shouldn't.
I used to own a skateboard and snowboard shop in Vancouver back in the 90's. Snowboarding was still in it's infancy and most companies sold direct to cdn retailers. We had a strong mail order business and could compete across north america on prices. Then as the industry grew, manufacturers looked to bring in cdn distributors. Canada was a small market and would rather just sell to a distributor and not have to worry about all the hassles of warranty, currency and what not of another country. Instantly our merchandise costs went up 20 to 30%, it was staggering. no longer could we compete with Mailorder in the states. There were actually some shops like CCS that I could buy stuff for the same price as my cdn wholesale. It's really ridiculous how hand cuffed our cdn retailers are and how they take the blame.
I try and buy local but at the end of the day, if it is significantly cheaper, I have to go with the best price. I was in my local camera store today buying some triggers and apologized to the Manager for buying my 5D at beach a few weeks back, I felt bad but told him it just didnt make sense to buy it Canada. He understood, he said he would of sold it to me at that same price if he could but it would be impossible.
I bet you if Canon mandated US and CDN wholesale to be the same, we wouldnt need them imposing cross border restrictions. I would be interested to hear from some cdn canon retailers.