Check with Border Services, both Canada and U.S. for their requirements, probably rabies and health statements. Even if the requirements are there, the agent letting you in may ask for them or may not. If you have the required paperwork, no problem, if you don't have it and find out you need it , oh oh.
If you see the vet regularly, you may already have it. On my yearly visit, they give me a statement, that includes the rabies vaccine, and any other pertinent information, healthy or other things done. And of course, the bottom line $$$.
Your 4 legged family member, returning to the U.S. is treated the same as mine, going for a visit.
Ken
2006 Winnebago Outlook 29B E-450.
2012 Honda CR-V AWD
Blue Ox Aventa LX tow bar and Brake Buddy Vantage.