AmIndHistoryAuthor
Banned
The numbers of escaped slaves before the ACW was never even close to enough to end slavery. It wasn't that easy to escape. They could get past the plantation owners easy enough but there were also slave patrols, dogs and bounty hunters to evade and very few knew the land more than 20 miles from home, at the most. There was in effect a general strike because 1) The Union armies were near at the end of the war 2) Most of the overseers and plantation owners were in the army or dead 3) Which meant that you had a lot of plantations run by women at the end most of whom were not capable physically or mentally to try and control hundreds of men on their own.
That's why I was talking about after the ACW. If we presuppose an early CSA victory, what you say would be true, say a CSA victory at 1st Bull Run that leads to a march on DC. But most timelines imagine a CSA victory several years in.
IOTL the issue of escaped slaves was enough to enrage both slaveowners and abolitionists for decades. If the scale of the number of escapes keeps growing, as they did in Brazil IOTL....