Maybe try to knock some of that rust off the hub snout, but get a micrometer or something on the hub and the wheel and see what the difference is. FWIW, just to reiterate in case it hasn't gotten through, there is NO DIFFERENCE between Canadian and Italian slicers as far as fitment is concerned.
See if the hub bore on the wheel has gotten distorted for some reason. A bend or ding on the wheel hub bore would also prevent it from seating.
Otherwise, somebody may have put the wrong hub in, but if the Italian wheels fit, the Canadians should fit fine, too.
Quick edit: the other thing to check is that the knurls on those studs aren't too fat. There have been problems with some aftermarket hubs having studs that are too short (for some wheels) and have thicker knurls than stock.