Are you serious dude?!? how can you compare the schools up here to 'lower tier schools' I can speak for the Ontario schools when I say they are definetly ON PAR with the ivy leagues down south! the University of Toronto was the first medical school to discover/implement the use of insulin!!! Queens, Western & McMaster have amazing research facilities. Some entrepeneur just invested 110 million dollars on Mcmaster. In addition, Harvard's PBL program was modelled on McMasters..... so I would definetly say that most schools here in Ontario are as good as the ivy leagues down south. In addition they are harder to get into... as us Canadians know.... if you have anything below a 3.70 (or more realistically a 3.80) Ontario schools won't even look at you...... the cutoffs for MCATs are also pretty harsh, look at Queens... you have to get at least a 10 in every section to be considered... and an N or is it a P in the writting sample section.
To answer your other question, yes it is possible for a Canadian to go to a US med school (hey I'm doing it next year). If you have any more questions just PM me and I'll be pleased to help you.