Art,I believe that they have, but I'm not as close to them as a Rick Fielding. If there are negative effects, Rick and other performers would know them. But all in all, I feel that the music industry which is dominated by American record companies would be just as happy to market exactly the same material north and south of the border. I believe that CanCon is at least partly responsible for the success of many of the artists mentioned here who may never have had a chance to be heard without it.
And CanCon also spawned SCTV's "The McKenzie Brothers" which started as a lark. There thinking apparently being "If you want CanCon, we'll give you CanCon."