he bungled things to the point where the nation was at war with itself...

Naah, Bobert - the Nation had been at war with itself ever since the Missouri Compromise of 1820 & Mason & Dixon's Line. Mexican War didn't help matters. The Compromise of 1850 only made things worse, as did the Dredd Scott decision & the Fugitive Slave Act.

The two sides were already shooting at each other in Kansas & Missouri in the mid 1850's.

Blaming Lincoln for the war is just like blaming Obama for the mess he was handed by Reagan, Bush I & Bush II.