Well, the criteria I have used is that a food is "Canadian" if it was invented or developed in what is now Canada (therefore, I'm including any foodstuffs that were developed or invented in any of the provinces of British North America prior to the Confederation of 1853), and is unique to Canada. I apply that same criteria when determining if a food is American, Mexican, Australian, etc.
Therefore, neither hamburger (originally developed in Germany) nor pizza (developed in Italy) nor French fries (which despite its name, was originally developed in what is now Belgium) are American, but are imports, even though these are widely consumed in the US.
Now to the rest of TERB -- is my criteria too restrictive?