While it's true that only France kicked out American forces, I personally heard people shouting "Yankee go home" and it wasn't just in France, either. It happened in Germany and in other countries. Perhaps you forget the "peace" protests of the 1980s. I remember them well.

As for stopping Hitler, Churchill and some others were pointing out the absolute folly of the appeasement process long before the Munich Conference. Unfortunately, some people would rather listen to a comfortable fiction ("Peace in our time!") than an uncomfortable truth. Time after time during the mid to late 1930s, Hitler gambled that the European leaders would be too gutless to stop him and he was proven right. The fact that he wasn't countered just fueled his popularity and even swung most of the German General Staff behind him. After all, it's hard to argue with success and the spinelessness and utter stupidity of the European leaders made Hitler seem infallible.