Undo one historical event?
The election of Obama.
Watergate. That led to the election of Carter. After that it was all down hill...including GWB winning....which led to Obama.
Agreed. We know the free world survived Hitler, despite the high cost. There is no indication that the free world will survive Obama, and I suspect if we survive the cost will be much higher than WWII. While the election of a totalitarian communist in the United States is a symptom of fundamental deterioration in our country, it is a dreadful symptom, and I would be thrilled if we could have avoided it. If I could somehow change the past, I'd pay a high price (cheerfully taking on Ebola, or giving up both legs, for example) for my country to be able to avoid this disaster.
Ditto that one.
The birth of Obama.