I suppose we should leave aside historical butterflies and turn the question to "What if America had a Bismarck-like President at some point between the 1860s and 1880s?" We kind of did: Bismarck admired Lincoln, who's been compared to Bismarck in some histories for unifying America and centralizing power, and Bismarck and Grant met and got along pretty well. The real question is whether *another* Bismarck-like leader would have had more of an effect on Reconstruction, successfully completing the Republican project of consolidating power in the federal government and breaking the old economic and social situation of the South. If someone with Bismarck's political abilities had replaced, say, Rutherford Hayes, could we have had a weaker South and less divided America heading into the 20th century? ...Maybe, but the forces against him would be severe? Or would Bismarck's social conservatism in an American context turn into more lenience for slaveholders? (At Bismarck and Grant's meeting, they had a brief dispute, with Bismarck insisting the main goal of the Civil War had been to preserve the Union, and Grant pointing out the importance of ending slavery.)