@Colonel-Mustard
I haven’t done Sealion in a game with another player, only in games where I play both sides.
My view:
The German air force might be heavily depleted from both the attack on the Allied navies and possibly the attack on London (anti-aircraft artillery). The Germans won’t be able to make that many new air units because they would be too busy taking on the Soviets (and they might need their remaining air units).
Generally speaking, depending on how much the Luftwaffe is used (especially if they’re used against the Allies in the Mediterranean) they won’t have enough aircraft to meaningfully threaten the US fleet (and with only a minor industrial complex in London, casualties beating the British, and resources in eastern Europe, not much can be dedicated in ground units to stop the US).