I’m not convinced the factories would necessarily help Allies. If Allies can’t afford to protect them, they become liabilities.
A huge difference in AA50 versus previous editions is how seperated/well-defined the two theatres of war are for USA. Once in one of the theatres, it is very hard if almost impossible to move into the other theatre while still being useful. An example of what I mean may help. If USA can establish a presence in the south pacific, either via a navy (hard to do early) or via Australia, she can land fighters into India for support. Put an IC in Australia to cover these fighters, providing defense on their way to India, where they would again provide defense to yet another IC, and then onto their way to even threaten the middle east with units that have began to filter in from combined UK/US Algeria landings
If UK is pumping ipcs into South Asia it may provide Germany/Italy opportunities in Africa and Europe.
Yes, it would be somewhat of a fine Allied balance, but the US can help Africa landings easier than building a naval force strong enough the threaten the IJN. Supporting Australia/India with fighters (see above), keeps $5 more in UK coffers (Australia/India) and the third NO out of japans hands. That’s a $15 IPC swing that more than makes up for less pressence in Africa/Europe.