In reading about "TL 191", I was reminded about how the USA was not always the stable world superpower we know today. There were events such as the civil war and great depression that were really hard on the Americans. During this time (I'm thinking 1860s-1940s) there was a lot of turmoil that brought about the rise of totalitarianism in much of Europe, and the USA was by no means unaffected by said chaos.
So what events and historical turns would be needed to create a true American dictator in the style of Hitler, Stalin, Mao, or Mussolini? What kind of ideology would such a ruler use to control the people? Could a lasting CSA prompt the rise of a northern autocrat? How would the politics of an undemocratic US affect its culture and politics into the latter part of the 20th century?