We are the Fenian Brotherhood, skilled in the arts of war,
And we're going to fight for Ireland, the land we adore,
Many battles we have won, along with the boys in blue,
And we'll go and capture Canada, for we've nothing else to do.
-- "Fenian soldier's song"
145 years ago the Fenian incursions into Canada took place. Erie Raid, May 31, 1866.
Here are some historical what ifs.
1) What if the US had not invoked neutrality?
2) What if the Fenians had been successful in their attempts on Canada?
Many historians consider the answer to both questions to be the same: Ireland would have been free of England a century and a half ago, and Canada would have been annexed by the United States.
Given the many questions that resulted from the actions as they were, it is little wonder that US-Canadian relations were a bit cool until WWII.
"Here Comes that Damn Green Flag Again" by Michael Ruddy
"The Fenian Raids" The Manitoba Historical Society