We are leaving out of VCE in July, 2015 and coming back to Los Angeles through Montreal on Air Canada. Do we go through customs in Italy, Canada, Los Angeles, or all 3? We went to Ireland in 2014 and were surprised by having customs in Dublin, not in Los Angeles.
You sure its not Toronto? I don't see any AC flights direct between VCE and YUL. Any way, if it is direct back to Canada, you will get your passport stamped exiting the Schengen zone, then arrive in Canada, clear US immigration (passport stamp), collect luggage, go through U.S. customs, recheck luggage to LA, go through TSA security, then get on the flight to LA. No formalities in LA.