I think it's going to be pretty hard to differentiate between Canadian and American. To me, the two sort of blend together. I also think we need to know what the purpose of the types of food you're planning on importing would be. If you're just planning on selling it in a supermarket for homesick Canadian and American expats in HK, there are a couple of options already available:
Hong Kong Hustle » Hey Kool-Aid! American junk food in H.K.! - Hong Kong nightlife, street fashion, culture, and cool
Off the top of my head, some things I wanted from Van which I couldn't get in HK were:
- Solid deodorant
- Certain chocolate bars (Mr. Big)
- Doughnuts (although I wouldn't imagine you would ship these)
- Canadian beers (although you could buy them at CitySuper for some ridiculous prices)