Update's done!
Part One Hundred Sixteen: The Great War Cometh
Cry Havoc:
While the Great War raged on in the rest of the world, events in North America continued to bring the continent closer and closer to the brink of entering into the conflict. With Great Britain embroiled in patrolling the high seas, pro-Irish and republican groups in the Laurentine countries stepped up the violence against the British government's arms in North America. The majority of these groups' activities tended to target the Canadian parliament, seen as the most supportive of London out of the Laurentine countries, and the various governors general of the dominions.
In the first months of 1908, there were two major attacks in British North America. The first was a pyroglycerin explosion at the Canadian parliament building in Kingston on February 5, 1907 just before the new session of parliament was to begin[1]. The bombing was similar to the bombing that took place at the Philadelphia Mint seven years prior. The bombing took place in the morning just as members of parliament were assembling in the building, and in the blast two MPs and nine others were killed with dozens more injured. Just weeks later on February 28, the governor general of Acadia was assassinated by three gunmen. The assassination of the governor general caused yet another diplomatic incident between the United States and London as the men who carried out the assassination were part of an American pro-Irish group known as the New Fenian Brotherhood.
The New Fenians were started by John Devoy and John O'Mahony in the United States in 1873 in New York City[2]. With many Irish Catholics migrating to the Americas, many settled in major American cities and formed clubs to promote their Irish and Gaelic heritage. These communities were also hotbeds of anti-British sentiment and called for support for Irish independence. However, after the Irish diaspora quickly grew, many groups including the New Fenians switched to calling for an independent Irish state outside of Ireland. The logical location for the state was Acadia, since it contained the largest proportion of Catholic Irish in the diaspora. Devoy and his New York group expanded to other groups around the country, sending money to pro-independence groups in Acadia. After the assassination a call was made in London and by the Acadian and Canadian governments to president Roosevelt to disband the New Fenians, and extradite one of the gunmen who had managed to reach the United States. The Roosevelt administration refused and though the gunman was placed in custody and imprisoned the British government remained unsatisfied.
Let Slip the Dogs of War:
While the events in 1907 and 1908 had strained relations between the United States and Great Britain and inching the United States toward joining the Alliance Carolingien, the United States was reluctant to enter the conflict. President Roosevelt was more concerned with domestic policy concerns and dealing with his reelection and handling the complicated balance in Congress. The president's memoirs indicated that he had fully intended to enter the war in 1909 should he be reelected.
However, that plan changed on April 19, 1908. During the end of a visit to Buffalo as the president was boarding a train, the assassin Drew Duckworth[3] fired four shots at Roosevelt from the platform. One of the shots hit the president, but did not severely wound him. As onlookers rushed to Roosevelt's aid, he waved them off, instead directing them to go after Duckworth. Duckworth was apprehended in the station while Roosevelt quickly recovered and calmly boarded the train. As a crowd gathered on the platform, Roosevelt came back to the door of the car and gave an impromptu speech. The exact words of the speech were not recorded, but the president assured the crowd that he was fine. Gesturing to the wound, the president recalled hunting for elk in Colorado the previous summer, and that "it took three shots to take down a bull moose. It'll take more than that to take me down."[4] The train's departure was delayed as a doctor determined that an x-ray should be taken. After an x-ray was taken doctors determined that the bullet wound was not serious. The bullet was not removed as the procedure was deemed to be more dangerous than leaving it in[5].
Rumors quickly spread throughout the country about the assassination attempt. One of the more popular ones that took hold was that Duckworth was a British spy. There was some evidence to this as Duckworth was a Canadian citizen and had frequent correspondence in London even during his brief stay in Buffalo leading up to the assassination attempt. However the British government denied these allegations and the extent of Duckworth's involvement with the governments of either Canada or Great Britain has never been released. However, the media ran with the allegation and during Duckworth's trial he seemed to enjoy the attention and played up the spying. Duckworth was eventually hanged later in 1908, though his sentencing was postponed until after the election.
The assassination attempt had a major impact on both the election campaign and foreign policy. Roosevelt did not betray any worry over the fate of the administration at the time of the shooting, but it became an issue for the president later in the campaign. The assassination attempt made the president rethink the role of the vice president, and in private letters he revealed that he was considering replacing William Hope Harvey on the ticket with someone stronger. At the 1908 Progressive convention, Harvey was indeed replaced on the ticket by Secretary of War William Howard Taft.
In foreign policy, the assassination attempt was the final trigger to get the United States to join the Alliance Carolingien and bring North America into the Great War. During Duckworth's trial, many prominent newspapers emphasized the assassin's ties to Canada and Great Britain in order to stir up public support for entering the war. Joseph Pulitzer in particular used his ownership of the Saint Louis Post-Dispatch and the New York Herald to drum up support for a war. Frequent articles were published embellishing the details of the Drew Duckworth trial and his ties to the British government. Editors such as Pulitzer also promoted stories of atrocities against Anglo settlers in California and pro-independence activities in the Laurentine countries during these years. With growing public support for entry into the Great War, Congress passed a resolution declaring war on Great Britain and her allies and colonies on May 24, 1908.
[1] Remember that the Canadian parliament was divided between Kingston and Montreal.
[2] Devoy founded the Clan Na Gael in OTL and O'Mahony founded the OTL Fenian Brotherhood. It's called New Fenian ITTL because of the idea that Acadia was a sort of New Eire.
[3] A cookie for whoever gets what the name references.

[4] Fun fact: Roosevelt would often spend summers in Glenwood Springs, Colorado in OTL, and during his presidency and Taft's the Hotel Colorado there was called the White House of the West. I was there a few months ago for the weekend and wanted to include it somewhere.

[5] And because Teddy just isn't Teddy without a bullet in his chest.
