they could if Canada has more cultural influence than the UK.
If I am not mistaken, American Idol was based on "Pop Idol" of the UK, and then there is something called "Canadian Idol" which no one watches. In the English speaking world, the British still has a huge influence. A large number of American TV shows are based on British one,
http://en.wikipedia.org/wiki/List_of_American_television_series_based_on_British_television_series
hardly any based on Canadian ones (usually the other way around, ie: So you think you can dance - Canada, etc) There is Harry Porter, popular all around the world. In the literary world, tons of British writers. hardly any world famous Canadian ones.
In terms of cultural influence, Canada is insignificant, while the UK can still be quite influential. You expect the Britons to adopt to Canadian accent (which is hardly distinguishable from American accent)? It is like ask the Americans to get used to New Zealand English.