Just to clarify here, by "WC" you mean water closet, right? I'm not too sure many people would understand what that was, unless they are either old or know a thing or two about old houses.
Now, I'm living in the Toronto area, where they haven't had wc's for a long time, but if you go out west they were a bit slower on the uptake with indoor plumbing (rural areas even less so, we're talking not till the 50's here). So I would think many more people in western canada would understand that.
Also, I've lived in Pittsburgh and said bathroom all the time. Usually people just smirk but they know what you are talking about. I don't know about bank machine though...