Yeah, our story isn't nearly as interesting as the American Revolution.
Short version of events to which I'm referring went as follows: the Union (North) had won the American Civil War by April, 1865. After some resettling/picking up the pieces as tends to happen after any war, the Union still had a large, hardened, professional standing Army in and around New York State.
This made Britain nervous because it was known by the Americans that Britain had bet on the wrong horse: with a vested interest in seeing the United States collapse into chaos, Britain had supplied munitions to the Confederacy from the eastern colonies of Nova Scotia, Lower Canada (Newfoundland today) and New Brunswick along the eastern seaboard by sea.
Keep in mind that these colonies were largely Loyalists, many of whom whose ancestors had settled there after America won Independence.
Toronto bankers, also British colonials, helped finance this whole business and Abraham Lincoln knew that, too. In fact, he wanted to attack Canada during the Civil War because of it but he knew that fighting on two fronts would be catastrophic for the Union.
So in light of all this, Britain figured that America might take another run at Canada after the zero-sum outcome of the War of 1812. Britain's professional Army in the colonies of Canada was expensive, and the colonies were run by British subjects after all, so after floating the idea around in Canada between the Premiers of the colonies, it went to a vote among the people living there, with the first four Provinces of Canada (New Brunswick, Nova Scotia, Ontario and Quebec forming Confederation in 1867).
The key detail; however, is that the British North America Act that defined Confederation and thus the Dominion of Canada was enacted by the British Parliament on March 29, 1867, not even in Canada. It came into effect on July 1 of the same year.
Fun fact: of the four founding provinces, Nova Scotia was unique in that their Premier at the time, Charles Tupper, who had been elected in 1864, lied about the result of the general election regarding whether or not to join Confederation. He was promptly sacked come 1867 for this but still went on to become Canada's sixth Prime Minister from May 1, 1896 – July 8, 1896; the shortest tenure of any Prime Minister in Canada.
Fun Fact 2: The CBC (Canada's BBC) ran a special show in 1982 to cover the repatriation of the BNA Act, 1867, that was ratified as the Constitution Act, 1982, under Prime Minister Pierre Trudeau. This particular document was so important to the British Parliament that they couldn't even find the original copy.
Edit (and somewhat unrelated but I think this is so interesting)--
Fun Fact 3: Ontario's first Lieutenant Governor (hey - just found a dialect similarity, we also pronounce the word lieutenant as "leftenant") John Graves Simcoe (1752 - 1806, was LG from 1791 - 1798) was a war veteran of the British side (obviously) of the American Revolutionary War.
Now Simcoe was no pushover and he was a brilliant strategist. In one particular skirmish, Simcoe and his men routed the Americans, forced them to flee. Simcoe's men wanted to destroy the enemy by shooting them in the back. Simcoe ordered his men to hold fire. The leader of the band of so-called American brigands? None other than one George Washington, yep, the George Washington.
How different might history have been but for that one military decision?