A simple move would have a huge impact on Canadian culture: removing American TV networks from cable and satellite. The reason this hasn't been done before is because of the proximity of the United States; residents in major Canadian cities like Toronto, Montreal and Vancouver can get over the air American channels. But this will change in February 2009.
In February 2009, you will need a converter box to receive what will then be digital signals (from the UHF band). Even with such a converter box, Montrealers probably won't be able to get a clear enough signal (I don't know enough about Vancouver to comment). Some Torontonians might be able to, but they will still need a digital converter box.
And since the vast majority of Canadians get their TV from satellite or cable, they are unlikely to invest in a good antenna and converter box to get the couple of shows that aren't retransmitted on Canadian networks. In addition, much of the quality American shows are now only available on cable TV networks.
Advertisers and Canadian stations would win because they would no longer be loosing viewers to American stations. Cable and satellite providers would win because they wouldn't have to worry about overlaying Canadian feeds when shows are also present on a local Canadian station. US networks would win because their products would no longer be shipped across the border for next to nothing (I think Canadian cable and a satellite companies currently have to pay a small amount for retransmission rights).
French Canadians culture would win because a higher percentage of stations would be in French. Canadian culture would win because it would be competing against more expensive American shows (well, the good shows would be more expensive, the bad ones would be just as cheap).
Canadian networks would win because they would be in control of what to play and when. They could put a Canadian show at 8, an Australian show at 9 and an American show at 10, if that is what will generate the most viewers. This is even more true in parts of Canada that aren't in the same time zone (Atlantic Canada).
The alternative, in my mind, is allowing foreing networks to broadcast in Canada (why on earth, for example, do BBC Canada and TV5 have to provide Canadian content? How does that make any sense?