American political parties are much more like broad coalitions than their Commonwealth counterparts. If a candidate is vaguely left-ish, supports high taxes, extensive government services, and/or is sympathetic to minorities and foreigners, they will likely run as a Democrat, whereas the small government and/or traditional values and/or America fuck yeah! candidates are more likely to run as Republicans.
The media only covers the party's leaders. I mean, Toronto has dozens of elections for mp seats, which should the Star cover?
The party the receives the most elected MP's across Canada wins, and their leader becomes the Prime Minister. The party votes for their leader, so Canadiens have little say there.
Sadly, most people vote based on who they want as prime minister, and they put little thought who is running their riding.
This is entirely rational, though. The local MP has two primary functions - one is to vote on legislation, and the other is to support a particular set of MPs to form the executive government (personified by the Prime Minister, because the PM usually gets most of the say in who makes up the remainder of the executive).
Both of these are important, but the choice of executive normally has far more effect on the day-to-day running of the country (and the executive mostly gets to set the legislative agenda anyway), so it's no mystery why people tend to focus on the choice of executive when deciding which local MP to vote for.
The party whip rules with an iron fist - votes where it is safe for party members to vote their conscience or directly constituents are the exception, not the rule. And my opinion is that a big reason for this is that individual representatives are basically anonymous here in Canada. They're too small to get any media coverage. The only time an MP or MP candidate makes the news is if they have a Cabinet position or if they make an apocalyptic gaffe. Debates, policy, etc. are ignored below the leadership.
No, there wouldn't. The electoral forces that drive duopoly operate the same almost independently of district size, changing the number of single-member House districts with first-past-the-post elections won't reduce duopoly.
Changing the electoral method might (and doesn't require changing the number of districts.)
Compare vs the blue dog Democrats that held up healthcare reform. That kind of party infighting is unheard-of in Canada.