YYZ is NOT MIA. Dear God, 3 hours is well enough to do this. It is the same terminal, and a long walk from level 1 arrivals to level 2 US departures. I arrived Wed night from SAL and was home in 40 minutes. (Of course I do not check bags)

Watch the Canada immigration lines - they are often a lot shorter at the end opposite where you come in and people are too stupid to walk there, and will stand in a line of 40 people while they can see a line of 3 people in the same room. Amazing to see. But capitalize on it.

It is also not a hike between the terminals for two reasons - one there is a subway now between T1 and T3. Two, you are in the same terminal for arrival and departure.