US, Canada, & Mexico all recognize drivers license's from the other two countries. There is no need for an International Drivers License. If you are legal in your home State or Provence you are legal in all three countries.
However, when I'm traveling in Canada, I inform my insurance company ahead of time, so they can send me a 'proof of insurance in Canada' card. I believe this is because the minimum limits are different between the two Countries.
I used to carry an International Drivers License for my trips to Europe and the Mid-East, but no one wanted to see it. They always asked for my US license, so I stopped carrying the International one.