The AI tends to play better on defense. The way the AI works is that it is set objectives within timeframes. So long as the game-date remains in these timeframes, it will continue to send assets against that objective, even if it does not have sufficient or appropirate assets to secure the objective. This often results in the AI's forces being destroyed piecemeal. As others mentioned, it is best, when playing as the allies, to avoid being overly aggressive with the AI during the Japanese expansion phase- until June 1942 or so.
I recommened PBEM. These games are so much more enjoyable with the right opponent. You may find it frustrating to play against a very experienced player, though as the allies, there is time to learn and early mistakes will not doom you. Post a request seeking an inexperienced opponent. Oftentimes, these PBEMs with inexperienced players, do not last more than 4 or 5 months. That is OK. You will gain valuable experience for when you do find a reliable opponent to complete the whole war. I am happy, actually, that most of my PBEM opponents did not complete the game. I learned new things each time and am now able to play against very good veteran players, such as Apbarog, who is committed to completing the game.
Hey Aurorus, Bobo is looking for to restart the contest, did you notice?