Can I enter Canada on my Italian passport if my Canadian Visitor Visa?
You must enter and leave the country on the same passport. If you can enter as a visitor with your Italian passport, then leave with your Italian passport. I do not see any reason why you want to use US passport to leave. If you are re-entering the US (i.e. US Canada US), you can leave Canada with your Italian passport, then enter US with your US passport. This is a two-step process.