Bruce McCall rounds them up:
There are actually funny Canadians alive today, but all nine of them moved to the U.S.A., and once they got here they renounced their Canadian cultural heritage, the way Mick Jagger renounced his English accent. Mike Myers never makes Mountie jokes. Jim Carrey declines to send up the toonie, Canada’s hilarious two-dollar coin. You have to scour Wikipedia to confirm the Canadianness of Mort Sahl, David Steinberg, Michael J. Fox, Catherine O’Hara, Seth Rogen, the late John Candy and Phil Hartman, and that guy from that sitcom, you know the one. America absorbed Canadian comedians, or, Canadians would say, Canadian comedians absorbed America.* Lorne Michaels, the Darth Vader of American comedy, harvests all the comedic talent in his native land as ruthlessly as Major League Baseball loots the Dominican Republic of shortstops.
Max Fisher flags the Jim Carrey bit seen above:
Note that it’s only self-mocking on the surface: It’s actually a fairly cutting portrayal of American ignorance toward Canada. "You Americans might like to tease us," he seems to be saying, "but we’re laughing right back."