I'm fascinated by "what if" questions about history, and it is certainly true that history would be very different without WWI (probably the Soviet Union would have never happened; Hitler wouldn't have risen to power because of an economically devastated Germany, etc.), but in terms of the creationism debate the connections seem a bit weak.
One of the authors writes that without WWI, William Jennings Bryan wouldn't have resigned from the Wilson administration and probably wouldn't have played a role in the Scopes trial. Another says that WWI caused an increase in textbook costs and explains that Scopes wouldn't have been using the "Civic Biology" textbook with its description of evolution had it been replaced as expected. Sure, but these are details. Maybe the "Scopes trial" wouldn't have happened in the same way as it did historically, but the same tensions would be there and simply be repeated elsewhere.