OK, not sure that came out clear…
Example:
US has $38 to spend. They have 2 existing TRNs in the Atlantic.
US buys 1 TRN, 3 INF and 3 ARM for the Atlantic, leaving $6 IPC, which they save.
The next round, the US has $38 to spend again, plus $6 saved from last round, and now have 3 Atlantic TRNs.
They buy 1 TRN, 4 INF, 4 ART for the Atlantic (4 loaded TRN). With the $8 remaining IPC’s they buy a TRN or SUB for the Pacific.
Round 3 with $38 to spend, they buy 4 INF, 4 ARM to refill their Atlantic fleet, leaving 6 remaining.
Round 4 with $38 plus the 6 remaining, they buy 4 INF, 4 ARM to refill their Atlantic fleet and add a DST to the Pacific.
This strat assumes a solid UK, no cross-Pacific push by Japan, and typical moves in Europe and Asia.
If you start out with this strat, by mid-game, the US has floated a fair navy in the Pacific for Japan to contend with… prior to them massing for a final push on Moscow…