It also depends on how much data you plan to use. Just judging by how many devices you plan to lug around it sounds like perhaps a lot.

For Canada I think it's kind of hopeless. I've gotten myself a Rogers SIM and pay the $7/week for week-long trips -- sometimes I have to pay twice because I exhaust the allowance in a few days. But the SIM isn't cheap to begin with and the call rates are so high on pay-as-you-go SIMs that you really have to use voip or google voice on wifi or else you chew through money pretty quickly.

You should actually check with your US provider how much it costs to buy Canadian roaming for the trip, it might not be much less than Rogers. There's also Fido but Rogers bought them and I think they have the same rates now.

For Germany I have no first-hand knowledge. Some European countries hand SIMs out like water (the UK, Ireland, Portugal) and some make you show some local address to get them (eg France -- though it's easy to bypass). My suspicion is Germany would be more like the latter.