I work in Canada a lot and have previously researched this topic pretty extensively. For simplicity I've found Verizon offers Nationwide Plus Canada. The "calling circle" or "5 friends" etc that most US providers offer only works while in the home network - Canada is roaming.
Mobile phone service is very expensive in Canada vs the US and I'd suggest you use your US phone and change your plan accordingly.
If you haven't already, don't use your US cell in Canada without making said changes as you'll be dinged somewhere north of a dollar a minute.