1) Confederates perfect/steal copper spinning technology in 1863, allowing them to easily copy bullets for the Henry Rifle. They had already knocked off the gun, the bullets became the serious problem. Gettysburg could still be lost but overwhelming Confederate firepower in late 1863/early 1864 could put a damper on the election and give the Rebs some breathing room.
2) Change secession by 5 years either way. Later means better defensive military technology for the South and a chance to develop railways, earlier means more dependence on Southern cotton for UK industry and less railways for the North.
3) Union invades KY first, KY secedes and Union forced to commit more troops to the area. Maryland continues to try secession and generates bad press for the Union, combined with Trent Affair UK jumps into the fray.
4) France alone decides to support the CSA.
2) Change secession by 5 years either way. Later means better defensive military technology for the South and a chance to develop railways, earlier means more dependence on Southern cotton for UK industry and less railways for the North.
3) Union invades KY first, KY secedes and Union forced to commit more troops to the area. Maryland continues to try secession and generates bad press for the Union, combined with Trent Affair UK jumps into the fray.
4) France alone decides to support the CSA.