The Americans like this narrative a lot, probably because it's a good excuse for preemptive interventions.
However, I don't think "appeasement" changed anything in the course of events except for holding up the outbreak of the war for one year. If the other European powers and the US had tried to isolate Hitler at the time, do you really think Hitler would have been cowed? On the contrary, it would just have been better for his propaganda machine and he wanted to start the war earlier anyway. And the idea of a massive military intervention to throw Germany out of Czechoslovakia is something that you may justify in retrospect, but at the time it would have been an absurd move, even it had had with popular support.