I agree with you. The manufacturers can always setup rules, but then consumers can also file lawsuits against them because North America has a free-trade agreement.
Also, there are work arounds too. For example, like some suggested, Canadians can buy used cars. Say 1 or 2 years old cars. Those are still under warranty, and yet much cheaper. The only drawback is not much choices to choose from.
It is called the Invisible Hand in the economy, especially when Canada and U.S. are so close together and its boundary is not as well-define as other countries (like U.S. & Mexico). Most of the people tend to put U.S. and Canada together when they mention either one. So, even the definition of "market" (Êг¡) maybe north America, instead of just U.S.
Yup! That's call Invisible Hand, or more common one, "Money talk!"
Let's look it at this way.
If it is the manufacturers who are the one set the prices that high in Canada, then eventually, the dealers will complain to them and ask them to lower the price. Manufacturers will have to comply because they need the retailers (dealers).
If it is the dealers who are the one create the high prices and they complain to the manufacturers (about people going to US to buy cars), then the manufacturers will just "keep one eye shut" because either way they will make money.