Just some general thoughts, nothing too specific.
It looks like the Axis left a lot of UK ships alive, so Britain can just plop down a carrier or two and be protected for a long time. Also, it appears the US Battleship in Hawaii is still alive, that’s awesome. Pull the US fleet back to California and consolidate, beef it up a bit (including at least one transport) and make Japan have to worry about that threat. It takes a little steam out of their Asia offensive. On the Atlantic side, use US bombers and transports to harass Germany, using the strong UK fleet to protect your transports in the Atlantic.
It seems to me that the US buying only bombers is a one-dimensional strategy that won’t have a huge impact beyond strategic bombing, but that’s marginally worthwhile anyway unless you get really lucky with the AA guns missing all game. Plus that gives Japan a totally free hand, which will usually sink the allies. Bombers are better when can also support a couple of transports to take France or other European targets, or when they can support your Pacific fleet. By themselves, they aren’t going to win the game for you, in my opinion.
Also, losing Karelia in the 2nd turn isn’t the end for Russia, so don’t defend Karelia unless you are going to win. It’s not worth losing 10-12 infantry just to do some damage to the Germans. Let 'em take it, but leave a large force adjacent to make Germany stack it. That will delay their offensive and possibly allow for breakthroughs elsewhere, and hopefully Britain or US can get a factory going in Norway to help that front a bit.
It’s tough to play Allies in this game, but you just have to be level-headed when it looks like you are losing and continue chipping away at the Axis until they crack. Do not ignore Japan or they will be making 70 per turn and pumping out 6-8 tanks in mainland factories in no time. If Japan has to buy ships to keep the US from attacking them, they can’t threaten Russia as quickly. If Germany has to retake France every turn, they can’t sustain an offensive against the Russians.
In short, the allies are all about making every little thing more difficult for the Axis, and hopefully that adds up in the end.