This isn't altogether surprising. As Christian Dufour observed in his 1989 The Canadian Challenge/Le défi québécois, modern Canada exists because it was created to oppose the United States, whether one talks of New France's role as French bastion against the Thirteen Colonies or of British North America's role as Britain's explicitly counterrevolutionary base on the North American continent. How did Canada loosen up? Tony Wilden's provocative 1980 book The Imaginary Canadian claims not, that throughout Canada's formative years Britain favoured the formation of a hierarchical society, as the Chateau Clique and the Family Compact demonstrate. Liberalism came from the south.
In Atlantic Canada, for instance, the Boston States exerted a tremendous influence. My parents have told me stories about anticipating the arrival of their American relatives, rich and well-dressed, giving them American dollar bills that they could redeem at the corner store for a Canadian dollar and change. (The exchange rate was different back then.) This experience was common throughout central and eastern Canada, judging by Ringuet's description in his Thirty Acres of the rich Franco-American relatives visiting the ancestral village on the St. Lawrence with their Ford and their jazz records and their love of baseball. Mass media--exclusively newspapers and magazines in the 19th century, electronic media in the 20th--played a hardly less important role. American influence was a breath of fresh air. Without the United States across the 49th, I'm sure that Canada would be rather more parochial than it is.
The United States is the sort of country that is good at destabilizing established conventions. This can be quite a good thing. Without the support lent by the United States after the Second World War towards multilateral rules-based international politics, in trade and elsewhere, I'm not sure if Europe and Japan ever would have properly recovered from the Second World War. There is the Argentine example, after all. American cultural influence in Canada isn't something that particularly worries me; uncontested American cultural influence does, but that's why it's incumbent upon Canadians to try to do something about the situation rather than blame others.
America has a vast amount of potential. Much of this potential has been used, and is being used, for good. Much of it isn't: Guantanamó, ground-penetrating nuclear weapons, Star Wars, greenhouse warming, the Religious Right. All of this potential, note, is controlled by people just like us. Non-Americans seem to tend to not trust American power; would we trust ourselves, though? I think David Bowie was hinting at this with his "I'm Afraid of Americans". I think that might be why I like this song.