Flag Thread I

Another map from yours truly, this time one made for an ATL version of Japan where it becomes a sort of less villainous version of OTL's USSR in a TL called Red Sun Rising (and no it wasn't made by me in case you ask):

Nice flag and so far i can tell you have not posted the Balance of Power timeline on this forum.

Nice flag.

Could they not survive as independent nations.

Back then Upper Canada (now southern Ontario) was very important to the Wisconsin territory and the area now known as the Upper Midwest. Ships brought lumber, raw minerals, grains and other agricultural products to ports like Collingwood or Goderich for transshipment to the rest of the USA (usually New York) and often to Great Britain, with a decent reverse flow of manufactured goods from factories. This route maintained its importance to the Upper Midwest economy into the 1870s when the rail network there was finally dense enough so that product no longer had to leave the USA as the fastest and most efficient way to get to the Eastern Seaboard states. From then on, only large volume stuff like minerals and lumber (for which ships and their larger individual capacities were still necessary) continued to be shipped through the Great Lakes though it increasingly stuck to US waters only instead of stopping at Canadian ports unless it was bound for the Canadian market.

If the rebellion had been successful in Upper Canada it would have been plum pickings for the USA to take and ensure that valuable economic corridor. Even though the Family Compact and their resistance to "responsible government" was what Mackenzie and his rebels were fighting against, their economic power would still be there after a successful rebellion. Just as they were squeezed out of public life OTL by the reorganisation into the Province of Canada and Governor Charles Thomson's reforms yet still managed to morph into the upper class Tory elite in Canada, I suspect they'd see an analogous transformation in an independent Upper Canada.

Even back then the Canadian economy depended on the USA, as things always are for the mouse beside the elephant, and the newly independent Upper Canada government would surely have seen that. It also helps that the newly independent state would have it's government packed with US-friendly rebels who would want to distance themselves from Great Britain to assert their independence. The Family Compact was IOTL nominally pro-monarchy but the fact that Governor Thomson thought it necessary to try and break their hold on Canadian politics shows how they were above all concerned with their own pockets rather than loyalty to the crown. As such, they'd probably support the Rebel's move towards closer ties to the USA, if only to not get hanged for treason at first and later because the economics were undeniable.

Thus the question becomes how forcefully would the USA "encourage" Upper Canada to become a state of the Union? The secondary question of that is how annoyed would slaveocrat states be at the thought of another free state as they were already twitchy about the balance and the possibility of slavery being banned from the USA.

  Very unlikely if the annexation wasn't widely supported in the relevant regions.  Quite possibly even if there was support.  Given the relative loss of face that would be involved.