Lincoln did create a new country. A new country not much better and in many ways a lot worse than the previous entity, except for the one thing, slavery. I put Buchanan as one of the worst presidents, others say Lincoln. But neither of these men would have been in the position to create the damage had not the founding fathers actually implemented the noble idea of the Declaration of Independence; that all men are created equal. A society cannot have equal men born as slaves. Slavery may have ended eventually based on it's inherant inefficiency, but when? In 1870. 1890, 1950? The Civil War was a bloody catastrophe and probably inevitable. If Washington and Jefferson could not or would not abate the problem, and they were truly great, wise men, who could?
As for Sherman, my grandmother was born close enough to the Civil War to have actual hatred towad Sherman. The effects of his actions were felt for a century. He also ended the war. Many lives were saved because of that. War is not beanbag. If people are to engage in war, and sometimes war is ievitable, the kindest act is to end it quickly and decisively.