In my first Europe game, the Allies won after 16 rounds. When the US liberated France, giving them 4 extra men and their economy back, they did help by attacking and taking Western Germany. The next round, USA was able to move through Western Germany and take Berlin. Germany was not able to properly defend it’s territories, even Germany itself, because of so much stuff committed to the Eastern Front. Moscow did eventually fall, but it took Germany a long time to get there and cost them a ton of units in the process. Plus, the very round Moscow fell, the US took Berlin.
One strange thing about this game was that London was never liberated. Once Germany took London, they built a strong force of infantry there and the US decided to bypass that to take Rome, liberate Paris and go after Berlin. The German navy was decimated and the Atlantic was totally controlled by the US so all those troops on England were pretty much stuck there. On the very last round, after taking Berlin, the US had enough forces left in the area and they liberated London. Technically the game was over though because the final German round to see if they could retake their capital had passed. It was really impossible for the Germans to retake Berlin because what was left of their forces were way east in Russia.
In my second Europe game, the Axis won in 8 rounds. So with those two games, it kind of goes along with history. Shorter game/war, Axis victory. Longer game/war, Allied victory. One big thing that did the Axis in was that they were planning on a short, quick war to achieve their goals. When the war dragged out, the greater Allied industrial and mineral resources told.