I will NOT thalk about how they won,but rather the consequences
What if the Italians/Romanians could hold their ground against the Soviet counter attack(with heavy losses) and the Fallschirmjäger captured the Baku oil fields(with severe damage though)
Meanwhile,the Japanese attack goes well,thanks to the changing of the naval codes(and Yamamoto does't die ITTL) and they lost only 1 carrier(compared to 4 in OTL)while US lost all three carriers
Could this be a game changer(if not for how many months these alterations will prolong the war?)
1.
Stalingrad: As others have said, a German conquest of the Baku fields in 1942 is flirting with Alien Space Bats. It's just beyond their reach, even for an airdrop. So I really am reluctant to address that possibility. But Stalingrad is certainly achievable, with a reworking of the deployments in Case Blue - as others have said, it could probably have been seized on the march. That will not allow the Germans to penetrate any farther into the Caucasus (not in 1942, at any rate), so the real question is what Stalin's reaction would be. Would he go insane and decimate his officer corps again, as Calbear posits in the Anglo-America Nazi War timeline? Would he engage in fruitless and expensive counterattacks to retake it or cut it off?
I think the probabilities favor a more modest version of that scenario. Stalin probably does exact some limited retribution with more 5 minute trials (and 9mm sentences) for certain generals. He will have every incentive to try to retake "his" city. German 6th Army redeployments to the flanks might well beat off these counterattacks, though perhaps at high cost (German logistics will still be stretched to the breaking point). Certainly it would make a mess, at the very least, of Soviet counteroffensives planned for the winter and spring, perhaps, buys the Germans as much as one more campaigning season.
The Allies would likely respond by stepping up Lend-Lease and TORCH to keep Stalin in the war. (
One more reason why TORCH cannot be butterflied away by a Midway defeat - in both Roosevelt's and Churchill's minds, keeping Stalin in the war is much more important than any harm Japan can do in the South Pacific in the short term.) They might even renew offers to stage assets into the Caucasus; Stalin might be desperate enough to accept them.
2.
Midway: This has been discussed so many times here...maybe the way to approach this is what I think you intend: how does the
combination of defeats at Midway and Stalingrad play out? Well, as I say: it's going to put more focus on saving the Soviets, because that is by far the greater strategic vulnerability for the Allies.
As suggested in the appendix of
Shattered Sword by Tully and Parshall, the heavy odds are that, after the destruction of Fletcher's carrier forces, an attempt is made by Kondo's force to invade Midway Atoll, and is bloodily repulsed at the waterline, with significant losses to Nagumo's air wings (already sure to be depleted in battle with Fletcher and Spruance), too. Yamamoto could probably scrounge up another similar size ground force from the Carolines and try again in a few weeks, but he probably would be content with having smashed American carrier power in the Pacific (for a little while). Midway would be difficult to take, and difficult to supply; it was too small to support a really robust air presence, and too far away from Oahu to be of much value to do anything to it.
Much more likely is the probability that Yamamoto sends the Kido Butai back to Japan to rebuild the air wings (along with that of CARDIV 5), and, sometime in August, tries to implement the first phase of
Operation FS in the South Pacific, while CINPAC is still reeling and the
Essex-class carriers are still yet to make their presence felt. A rapid move might net him Port Moresby before MacArthur's buildup; and Espiritu Santu could conceivably be taken. The danger for Yamamoto would then be to greatly underestimate American assets in the New Hebrides, and in his hubris, try for New Caledonia.
Which would be an utter disaster for him, even just counting forces present there on June 4, 1942. He would not only lose most of his ground force trying, but quite probably much of his carrier force as well. It's just a bridge too far.
Meanwhile, King would kill any idea of WATCHTOWER, and concentrate assets instead on building up on Fiji and the New Hebrides while he waits to reap the great Vinson Act production bonanza building on East Coast slipways. The great American counteroffensive would likely then begin in the Central Pacific (Gilberts) in early-mid-1943 rather than in late 1942 in the Solomons. The Solomons are probably largely island-hopped in this scenario.
Either way, Japan is crushed by 1945. It just happens a little differently.