Depends on a number of things.
Allies do not have a total unit value advantage, most of it is airbase/naval/ics. Catching up in income with axis is not hard, but you do drop when Italy gets convoyed out of the game. As long as axis take advantage of their position, they should win.
The biggest problem allies have is USA is 2-3 turns from doing anything in europe or pacific, so when you buy, you are buying because of what you hope things look like 2-3 turns from now. Since the allies are forced more or less into a containment strategy (where you prevent the axis from winning rather than rushing a capital), it is hard to stop an axis win from either side.
I applaud Larry Harris for making people do pacific in a global game, but it is hard to balance the concept.
The J1 DOW gives the illusion of a rich USA that can do whatever he wants, but in reality nothing changes except japan took islands sooner than later at the expense of taking ground forces off of Asia. That is it.