"During the Civil War, Irish-Americans in the North planned to capture Canada as a retaliation against British support for the Confederacy. I think they were called 'Finnian troops' or something."
YES! You're correct! It's one of the least known chaptes of Civil War history -- both the French & British colonial empires wanted to see the Union dissolve so they could "divide and conquer," the way they did w/the rest of the world (esp'ly India).
Canada, @ the time, was not a Confederation like it is today, but a series of separate British crown colonies (like we were before 1776). They were so concerned over the possibility of a US invasion after the Civil War as "payback" for the British Empire's support of the Southern states that representatives from each of the Canadian colonies met on Prince Edward Island to pull the colonies into a confederation, w/Queen Victoria as head of state. This came to fruition in 1867. This is why Prince Edward Island is called "The Birthplace of Confederation," and the 9-mile bridge connecting it to the mainland is called "Confederation Bridge."