Cal, there may be some other requirements--though my cousin, an architect, only needed his degree (Dalhousie) and license (Albert and BC) to accept a job in CA as an architect. Here is the relevent information...
There may be other requirements to practice, such as passing specific aspects of a provincial exam, but if you have a US PE you can get hired, without going through immigration, as a PE in Canada or Mexico, and vice versa.