What if the Brittish and the French hadn't bothered to appease the Nazis in 1938? Would things have turned out anything like Turtledove's War that Came Early series?
I don´t know Turtledove´s work but it is often discussed , that there might have been a military putsch by Wehrmacht elements against Hitler. indeed, there was already a plan to remove Hitler in case of war , but was cancelled after news of the agreement.
If France and Britain had declared war, Italy might hve been on the allied side ? Perhaps there would be a broader coalition against Germany in Europe ?