NoNukes writes:
Even after secession, the issue of what would happen in the territories and what was to happen to runaway slaves was probably going to lead to shooting.
What led inevitably to shooting, in my humble Canadian opinion, was the fact that the states had their own armies ("militias"). In Canada, the provinces can disagree "violently" with the federal government or with each other but they can't do anything about it.
Maybe the Civil War was God's punishment for having a flawed constitution.