Answer:
The British Involvement
Britain was engaged without proclaiming which side they were on. The south relied on the protection of Britain, but they did not get it. The British Government needed to help the Confederacy. British common people were anti-slavery. British had a sufficient supply of cotton and did not need the South for that supply.
Given bad crop yields, Britain was pressured to import grain from the North
The Trent Affair
First major crisis in late 1861, with Britain. A British ship was stopped by Union warship and 2 Confederate Delegates removed. Slow communication has given UK time to calm down.
Alabama
British made a Confederate Warship. The ship picked up arms in Cuba. Union merchant ships were captured and burned. Canada was invaded by the north.
Laird Rams
Two huge warships made in the UK. Fabricated to sink Union ships. Had they supported the West, Canada would have been overrun by the East.