Does it have the Kenwood Head Unit? If so, it is probably that cage that surrounds the actual unit. I had to remove mine and bend it down a little bit. Next time you are driving down the road, try pushing on the face of the unit and see if it goes away.
You'll find a lot of differences between the US models and the Canadian ones besides MPH.
But you could try pushing on different areas of the dash while driving. I had a rattle that I thought was from the dash or the passenger door and it was actually from my sunglasses in the sunglass holder. Sometimes the sound isn't from where you think it is. Have you had friends try and locate it too? Once you get it narrowed down then take it in. The dealer will just take it for a drive and if they don't hear anything they won't do anything. If you can narrow it down for them you'll stand a better chance at having it fixed.