I think you're right, both of those events would be very unlikely to lead to a Civil War reminiscent of OTL. I listed those flashpoints to point out events that WOULDN'T lead to an OTL style Civil War. I guess I wasn't clear enough, thanks for pointing that out. I'm asking if there are any other events, besides those listed above, that may touch off an early North vs South war over slavery.
Oh, I see. It seems I misread you, btw. My apologies.
Well, there is one thing: the U.S. takes at least a little more of Mexico after the Mexican-American War, and, preferably, under someone who isn't James Polk; if the Wilmot Proviso, or something much like it, goes through, as many Northern advocates of Manifest Destiny had hoped, then it would permanently deny the South their only real shot at expanding slavery westwards, beyond Texas. And with even more potential free states, it may help spark the Civil War a full 4 years earlier than OTL, especially if a guy like John Fremont or William Dayton ends up in office.