1. Scramble all UK aircraft on the G1 attack. Sink as many ships / shoot down as many German aircraft as possible. As this is vital to the Axis strategy of leveraging a Navy and aircraft from Gib - the less they have of them to stack up the better.
2. Suicide your Med fleet to cripple the Italian fleet. Again, if the Italian navy / air force is giving you problems, this is your best chance to do some damage now before it all stacks up off of Gib.
3. UK2 and UK3 can consist of 3 SS placed off of Canada, plus 1 Bomber each round placed on London. 6 SS and 2 Bomber (potentially 3 depending on what you did with the one in London) is nothing to sneeze at for a navy that probably has 1 DD off of Gib, maybe 2.
4. Save as much of your remaining navy as possible (IE the DD in SZ109/106, CR in SZ91). Position them off Canada or SZ83. These are both places the Axis navy does not want to go to hunt you down. The strength of the Axis is in stacking together in SZ91, and an aerial counter attack if you fail to reclaim Gib.
5. Sacrificing the starting UK TT to get 2-4 extra ground units on Gib will prove troublesome for an Axis trying to make a landing (Ger or Ita) with only a single TT.
6. Fly that French Ftr down to Gib.
7. Send the UK TT from SZ98 to Malta, snag the Inf/AA and drop them off at Gib. You do expose any surviving aircraft from the suicide attack on the Italian navy, but I’ll chance it if it means an expensive attack on Gib.
Overall that should get you something like up to 5 ground units on Gib + AA + 1 Ftr. Ground units depend much on what you lose to the Axis before you get to go. Its going to take a lot more than 1 Inf/Art on a TT to dislodge them, making it expensive for the Axis to take early.
You also position yourself with somewhere around 6 SS, 2-3 Bombers, 2-3 DD and maybe a CR to strike against a SZ91 naval presence by the Axis - and thats as the UK. No US purchase modifications necessary unless the Axis keeps spending on a Naval conflict it cannot win.
Just make sure you are able to finish off stacked Axis aircraft on Gib, or put such a severe dent in them the US doesn’t have to worry about its fleet being sunk sitting in SZ91.