As I recall, Sherman's feat required him to quit his logistics base, knock over Atlanta and then make for the sea to take on more food. Of course they foraged, or plundered, what meager scraps they found along the way. However, heavy rains could have turned the roads to mud and put him in a pretty sticky situation. I'm not saying the wouldn't have made it, they had lots of horseflesh to grill up, but it would have worn out his army badly.
Less mentioned are the exploits of Sheridan in the Shenandoah Valley of Virginia. Now, the valley was feeding Lee's army, so he could plead military necessity as he killed livestock, burned crops and wrecked barns, plows and anything else he could find. Without any meaningful post-war relief effort, this led to problems with malnutrition, disease, infant mortality, etc which persisted for many generations. Since the valley is fairly narrow, it is likely that the officers controlled the men better than in Georgia.
I keep coming back to the idea that the north based its actions on the idea that it was one country. By taking the war to the southern people, the Yankees more or less validated the south's claim that there really were two nations, and as the man with the beard said, "Let my people go".