It might. It would never affect saskatoons, because the only place that saskatoons come from, I believe, is Canada. In other issues, say with raspberries and strawberries, the factory I buy from buys all they can from Canada, but sometimes they can't always get the berries from Canada because of the market situation or they're not available.
My problem would be, well, maybe a lot of the time, or most of the time, the raspberries would be from Canada, but if the factory can't get them, do I then have two labels? Would one say that it's a product of Canada and another one say it's not a product of Canada?
As you said, Canadian jam is better than American jam. One of the things that makes it good is the fact that I can put “Product of Canada” on the label.