My comment on comparing Canada and Russia was based on weather not distance. While I know the cities are relatively close they are spread out causing the US to spread themselves out to launch multiple offensives. Still not easy for the US.
The weather is slightly warmer in Toronto and Montreal compared to, say, Moscow or Leningrad, but they get (slightly) more snow. Also, Moscow and other inland Russian cities have lower record lows than Toronto and Montreal, and one of these winters just so happened to be 1941-1942, the coldest of the 20th century and the one where the Nazis were at the gates of Moscow.
As for distance, the Great Lakes makes things a bit simpler, assuming naval superiority is won. The lakes were officially demilitarised after the War of 1812, so either the associated treaties are violated (if the US is likely to join Central Powers, this is likely), or they'll need to move enough ships to the lakes or build new ships. Canada and the US have their industrial cores next to the lakes, but I think the US would be able to churn out more ships than the Canadians. The Germans and Americans on the Atlantic will prevent any reinforcement of the Great Lakes and St. Lawrence from Europe.
Once the Great Lakes are secured for shipping, then you really only have 3 fronts of any real importance. The longest runs along the Vermont and New York borders to Lake Ontario and is about 425 km long. A lot of that is also the St. Lawrence River and Lake Champlain. That's a distance typical of the Eastern Front. The second is the 58 km long Niagara River, and the third is about 135 km long and runs along Lake St. Clair and the Detroit/St. Clair rivers. That's a total of 618 km, plus Lake Erie and Lake Ontario which I assume the British or Canadians will never be able to seriously contest.
The only parts of Canada that would actually be difficult to digest would probably be the Ontario peninsula and Quebec, but we'd probably spin Quebec off as a puppet republic and just take our pick of the rest. France loses for the second straight time, causing fingers to be pointed various ways. Britain's economy collapses along with France's. Germany carves some puppets out of Russia, puts military restrictions on the western Entente powers, takes some colonies in Africa and maybe Asia, takes anything with a German-speaking minority in France just to piss the French off (because
there's a good idea
), and starts throwing big lavish military parades and thumbing their noses at the Brits while playing loud marching music. Austria does...something to Italy to get payback for the backstab, something nasty that AH can't actually enforce without German help. Ireland goes free and is now America's bestest friend ever. Ottomans survive, say "yeah the only people we owe jack shit to now are the Germans, Americans, and maybe some Austrians", and get to work fixing their economy and military.
I don't think Quebec would be granted independence when the US wins, since the Quebec independence movement wasn't really born yet, but the experience of the war would drive such a permanent wedge between Francophone and Anglophone Canadians that such a movement would emerge much earlier that within a few decades, Quebec independence would be inevitable as the United States ensures a fair referendum occurs on it. IMO Quebec would probably end up a major source of collaboration with the Americans since OTL the Quebecois felt they were dragged into the war by the British (not that they were sympathetic to the Central Powers) and when faced with the wrath of the United States, would prefer to stay neutral rather than face the American invasion which would devastate Quebec.
In Western Canada, I suspect that the Queen Charlotte Islands would be annexed to the US, and probably parts of Yukon. I wouldn't be surprised if all of Canada west of the Continental Divide (most of Yukon and BC) became American, since there's so few Canadians there to begin with and a land route to Alaska is very nice.
Once Quebec gains independence, I suspect the Maritimes will gain independence too, leaving Canada consisting of Ontario through Alberta. This Canada could focus more on the affairs of the Western provinces to avoid the OTL disputes with Alberta and such. Newfoundland probably won't remain a British dominion. The Royal Newfoundland Regiment will probably fight in Canada or the Carribean, and will suffer a similar fate to OTL no doubt. If/when Newfoundland hits a financial crisis, I wouldn't be surprised if the US steps in on behalf of some politicians there and makes it a puppet state akin to what the US did during the Banana Wars. The US could make a better deal than the embattled, defeated UK.
Of course this entire situation is absurd because it'd take a LOT to get the USA to get involved (as it did OTL; it took the Germans repeatedly sinking our merchant ships as we repeatedly told them "don't sink our merchant ships, asshole" for us to get involved beyond grudgingly accepting IOUs from the Entente, and that was with an Anglophile president), but when we enter, the Central Powers wins in a year tops and America gets to carve up Canada like a prize turkey. I hear that the new state of Lincoln (formerly peninsular Ontario) is very nice in the springtime, and the state of Roosevelt (formerly Alberta) has some tar sands that might be worth looking at sometime if we ever run REALLY low on oil and/or don't give a crap about the environment.
True enough, but I think Central Powers US is a fun scenario, especially if you can buff the British and French to not fold within a year of it due to lack of US imports and the effect of the US Navy.
2. Utilizing your own numbers, the U.S. has 217,000 men to Canada's 78,000 which is a margin just shy of 3 to 1. Given the reality that all strategic areas of Canada are within a few dozen miles of the border and the sheer scale of said border, this advantage in force size means the U.S. can rapidly seize vital areas, especially given that Canada's forces are more apt to be guarding the east given the population centers. This means that targets like Winnipeg are ripe to be taken by the U.S. with all that entails for Canada. Further, I think it bares pointing out that only 0.039% of Canada's forces are professional soldiers while the rest is militia. Their value for offensives will be zero and I'd honestly question their value on defense, given the U.S. has nearly as many regulars as Canada has soldiers.
If the US is in the war, then not a single Canadian is going to Europe. No Canadian Expeditionary Force. Winnipeg might be 100 km up the Red River from North Dakota, but I doubt the US could actually do more than raid the outskirts in 1914/early 1915 given their lack of soldiers. I doubt the US could make any effective offensives for a year.
Of course as noted, a Central Powers US will have different military priorities, and Britain/Canada will react accordingly, including militarising the Great Lakes which will be responded to by the US.
