@Tutti Thanks for reading.
The original post addresses purchases after the US enters the war, once its industrial complexes have been upgraded and income is augmented by National Objective bonuses. Thus, “USA1” refers to America’s second turn after entering the war, which would be the first turn they have ~70 IPC to spend. Up to that point, my recommendation is to make those necessary “security” purchases - carriers, destroyers, aircraft, etc.
I understand your aversion to buying ground troops, only to have them sit for a turn while you buy transports the next. When the US is at war, you can certainly do several turns of 5x5x5 buys (5 infantry, 5 artillery, 5 transports for 70 IPC). I’ve done this many times, myself. If your goal is to assemble an invasion force - a force large enough to make a successful amphibious assault and survive an enemy counterattack - the 5x5x5 system will work just as well as the (10x10)+10 purchases I detailed, but only in the Atlantic. Because the US only has one IC on the Pacific, the (10x10) +10 is still the most efficient method of assembling a force to invade Japan.
As for the troops America starts the game with…they can easily be incorporated into your invasion forces, but I usually have other uses for them. To give just three examples: 1) I use the Atlantic transport to activate Brazil and shuttle the Brazilian infantry to Gibraltar or Morocco, 2) The American armor and mech infantry, when parked in the Western US, can deter Japan from invading Alaska, and 3) As soon as the US enters the war, I like to use the transport off Hawaii to capture the Marshall Islands. If the Japanese don’t have carriers within striking distance of Hawaii, taking the Marshalls eliminates the threat from Japan-based strategic bombers, allowing you to safely move undefended transports to Hawaii.
