Another KGF tip…
Use those starting AA guns in the US. They’re just sitting there doing nothing. Use them. Maybe you had the UK take France and the UK has a few units left in France. Have the US go drop another 10 in France behind them, and make one of those units an AA gun.
A warning though: Check to see if Germany can re-take France. If they can take it, how many units will they likely have left in France after the battle? If it’s low enough that the Allies can re-take it the next turn, then by all means throw everything in. It’s just a large trade. You’re exchanging UK and US units for German units and that wears Germany down. If Germany has enough where they can take it and then stack it so it can’t be retaken then be cautious and just drop a minimal number in.
For NW Europe, this is likely just 1 transport. For France, it’s more because it’s a 6 IPC value territory in the situation of a strafe. Sometimes Germany will have a lot that they can bring at France, but if they bring everything then it leaves them too weak elsewhere. For example, if they bring 25 infantry and some tanks to France to take it hard, then that would leave them too weak in Germany.
In that situation bring 3 transports to France to leave about 4 or 5 there. It’s too few for them to do a strafe because they don’t want to lose the income from France. It’s too many for a light trade, so you’re still getting your goal of a heavier trade.
You have to read the situation in Europe though. Sometimes it may even be worth it to have a negative net trade with Germany if it’s early game and Germany is pushing at Russia hard. It will divert units away from the eastern front.