This is because the word "Canada" is derived from the Iroquoian word "Kanata," which means "settlement" or "village." In French, the word for settlement ("établissement") is masculine, and this association is carried over to the country name.
So, when referring to Canada in French, you would use masculine articles and adjectives:
* Le Canada (the Canada)
* Un grand pays (a great country)
* Le beau Canada (the beautiful Canada)