Thing is, Subotai, we know that an allied SBR campaign can give the allies a strong chance to win. (4 Bombers for England + 4 Bombers for America assuming 1-2 bombers lost still gives you 21 IPC on average, but there’s also a good shot at taking up to 32 IPC from Germany.)
The question is if the Axis can also pull the same gambit. I would think that Russia would be far more susceptible to German and Japanese bombing raids than Germany is to English and American bombing raids. (Heck, it’s almost common to see Germany and Japan send their solo bomber in every round just to do 7 IPC damage on average, if 7 is good, 21 is thrice as good, right?)
As for the allies getting anything more than normal, I just don’t see it really. 2 Bombers for Germany is No carrier on Germany 1, plus three less tanks on Germany 2. 2 Bombers for Japan is no Industrial Complex on Japan 1, and no ships on Japan 2. reasonable sacrifices that should have no major impact on the game. (Honestly, I don’t even build Industrials with Japan until I am maxing out Japan every round with 4 Infantry, 4 Armor and I have 15 IPC left over.)
Don’t forget, this strategy starts you off with 2 free bombers at game start. So we’re talking about Russia needing at least 2 hits before the axis even loses a single IPC worth of equipment. The odds of 3 hits or more is less than 6% in one round.
Meanwhile, bombers have a big utility in forcing the allies to invest more in surface ships to protect their transports. This alone could offset any increase in allied potency for a few rounds at least. (I assume it would take an AA Gun at least 10 rounds to kill all 6 bombers, but that’s just a guess. )