Those Jewish rebellions were no big deal, right?
They were certainly a big deal to the Roman officials who were tasked with suppressing them and the affect they had on the Jews.
Big deal in the sense that's what brought down the Empire? No, not really.
So why didn't the border states join the Confederacy?
Well, for starters: Delaware is pretty straight forward. By the 1850s slavery in Delaware was confined to the extreme south of the state, with the majority of the state being abolitionist. Seceding from the Union was never gonna happen.
Maryland had a problem with geography; it had a long, largely undefended border with Pennsylvania that would've been impossible to defend. Furthermore, Maryland was pretty divided between northern and southern sympathizers, and while many of them did not support succession, some did, but martial law was declared in the state and used to round up most of Maryland's would-be Confederate leadership. The rest fled to Virginia.
Kentucky was weening off slave plantations due to it's economy moving towards tobacco, which required less manpower to harvest. Kentucky actually requested to stay neutral, which it did until Confederate troops took control of Columbus, swerving the state into the Union camp.
Missouri's top government officials were supporters of the south, but much of the legislature did not want to secede. The result was a short but complicated mini-civil war that ended when Governor Jackson declared his own Confederate state of Missouri that was actually recognized by the CSA, but Missouri itself never seceded.
So simply but most of the border states didn't secede because over time they had grown less reliant on slavery to support their economies. Without such a major issue at hand they couldn't justify secession, so they stuck with the Union.