The spread in riding (electoral district) size in Canada only varies by a factor of 4.5 if the (mostly unpopulated) northern territories are included (the three territories have one MP, each, to represent populations of less than 30,000) and a factor of 1.5 among the populated provinces.
Canadian federal governments are generally comprised of whichever party received the largest share of votes nationally. This is not always the case in the US.
I'm going to disagree with you on this. In Canada, the general votes usually result in 1/3-1/3-1/3 split between the Conservatives, Liberals, and NDP. It's our first past the post system for MPs that results in the uneven split at the final tally. The only reason that the system hasn't succumbed to gerrymandering as badly as elsewhere is that district changes must be prompted by a change in the number of provincial seats from the census. The changes themselves are proposed by an unelected third-party with members chosen by the judiciary of the province and the speaker of the house (who is chosen by the MPs through a secret ballot vote). Otherwise, it would be all too easy to gerrymander an election in Canada and end up in the same situation as the US.
Contrast this with countries that use proportional representation which means everyone's vote basically means more or less the same as anyone else's vote.
The US is currently ranked 25th in the world by "democracy ranking"
On the other hand, we do use proportional representation (single transferrable vote, STV) to elect the senators for each state, which is different from the first-past-the-post method the US uses. In a normal election, half of a state's senators are up for re-election; exceptionally, the government may call a special "double dissolution" election, in which the whole Senate is re-elected, if the Senate repeatedly refuses to pass legislation sent to it by the House of Representatives. Our use of STV means that minor parties (Greens on the far left, One Nation on the far right, various centrist/populist independents and other small parties) end up controlling the balance of power in the Senate. Some people don't like that because these minor parties end up sometimes extracting all kinds of concessions from the government in exchange for letting government legislation through.
I think some kind of unequal representation – like the Australian and US Senates – is essential for a federal system to work. Look at the United Kingdom – England has almost 85% of the population, so a big enough majority in England can always overrule the other three smaller constituent countries (Scotland, Wales, Northern Ireland), and there are no constitutional mechanisms to prevent that from happening. That's a large part, I think, of why the UK looks like it isn't going to last, with Scotland likely to break away sooner or later, quite possibly followed by Irish reunification some years further down the track, and once its just England and Wales, maybe even Wales will eventually decide to follow Scotland's example. If the British House of Lords was more like the Australian and US Senates, and gave the smaller constituent countries the ability to block an English-dominated majority, then the UK would be more likely to survive.
edit: CA accounts for 15% of the US GDP
U.S. is at place 25 and is categorized as a flawed democracy, lower than Canada and some European countries (but far from all).
Electoral college