A few random observations on points others have made -- I haven't been back to the site for a few days:
Accents: A book called "Speaking Canadian English" by Mark (forgot his last name; he wrote law textbooks in real life) makes the point that Canadian English is much more influenced by early immigrants from the U.S. than Canadians realize. Which may be why Americans find it easy to understand, and why Canadian newscasters get big jobs in U.S. television (e.g., Peter Kent, Ashleigh Banfield).
A TV series on The English Language made the point that Canadian English is much more homogeneous than you'd expect, given the small population in a large geographic area. Regional accents don't seem to develop, and what regional accents exist (e.g., Newfoundland, Ottawa Valley) are gradually heading towards the mainstream. This doesn't seem to happen in Britain or the U.S.
I speculate that this is because we have a lot of national institutions, both corporate and governmental, and they move their people around a lot. It's no surprise to find an R.C.M.P. officer from Newfoundland stationed in British Columbia, or somebody from Nova Scotia working in a Canadian Tire store in Alberta. Over a generation or so, the accents get smoothed out. I get the impression, without any evidence to support it, that Canadians are more prepared to move around the country than Americans or Brits. In a resource-based economy (mines, forestry, etc.), people go to work where the resources are.
Must leave -- back later.