The way Turtledove presents it? No. It wouldn't directly result in the destruction of the Union. The Battle of Antietam might play our differently, but McClellan outnumbered Lee nearly 2:1 in the battle. I highly doubt that it'll result in the destruction of the Union army, allowing the Confederates to steamroll.
The problem is, without the 191 incident, there won't
be a battle of Antietam; Lee would control the timing and placement of the engagement if there was one (engaging the Union in battle wasn't one of his objectives). Hardly a certainty when McClellan can still deceive himself into thinking he's facing two to one odds.
If Lee can posture like a larger force, sting the Army of the Potomac, and send Little Mac scurrying back to the Washington fortifications, the abandonment of Northerners to the ANV is going to seriously delegitimize the Republicans, and Lincoln wouldn't be able to issue the Emancipation if his main army was driven from the field on Union soil. Lee can resupply his army in Maryland, rip up Union railroads, and make demonstrations towards major cities in the Union.
I can't say whether it would be a war winner on its own, but preventing Lincoln from issuing Emancipation, bringing the slave population directly into the Union camp, and preventing any kind of British-Confederate cooperation is going to result in much more even scales for future campaigns.