I don't think it has anything to do with the host, at least in the sense that he calls for it. Canadian content is required for the show to air in Canada - hence the Canadian questions. Perhaps Trebek himself is Canadian content.
Second City faced the same issue so they ingeniously came up with Bob and Doug McKenzie's “Great White North”.
Strangely enough, on the May 25 episode, there was a Final Jeopardy question about U.S. geography that read: "Touching Canada at boundary county, the northern part of this state's panhandle has been referred to as 'the chimney'". Then, on yesterday's episode, there was a category about "Canadian places".