Repeated testing of the 9th AF with the the same air directives as 2 TAC showed that USAAF Groups are 'squishier' than RAF squadrons and lose morale faster. Even with very low aircraft losses. I see no good reason for this except some mathematical simplification in the game's code. Thus, USAAF groups were 'squadronized' by a Python script. This fixes the issue. USAAF organization was flight-squadron-group, so this feels reasonably accurate in a historical sense.
I've notice this, and wondered why. It may, indeed, be a math issue in the code, where larger numbers have a disproportinate likelihood of suffering damage or loss. For example, if you move an infantry division from Oran to Naples in short bursts, you have a good chance of getting all the way there without naval attrition, whereas if you do the entire voyage in one click you almost certainly will suffer attrition. I believe one of the designers confirmed this to me. The same might be true for 75-aircraft air units v. 16-aircraft units.
Cary