Manufacturers have always been free to sell different cars in Canada and the United States. The regulations are different - for example, Canada had daytime running lights a long time ago as a requirement in many of the provinces.
The practical reality is, that the Canadian market is relatively small, so tailoring vehicle distribution to a small market may not have been economically viable for a manufacturer.
Peugot, for example, left both the US and Canada at the same time. Creating a different vehicle to comply with different regulations in the US (as opposed to Europe), simply wasn’t worth it to them. They viewed the market as “North America”.
The perspective is shared across many European vehicle manufacturers. Volvo, for example, or Mercedes, talks about “North American“ vehicles, not US or Canadian.