I try to spend 70 % in the Europe Theater and 30 % in the Pacific Theater. This is my strategy for the total game. Turn 1 is a different matter, and this first spending depends on the situation on the map. Usually I would spend all money on ships in the Pacific Theater, or all money on bombers to SBR Germany, for Turn 1 only. Then continue with the 70/30.
Historically USA did spend 90 % in Europe and only 10 % in Pacific. But the cost of a real army seem to be higher than the cost of a real battleship. In the A&A games, its opposite. Infantry cost 3 IPC and battleship cost 20 IPC, so its different.
But the point is, the East coast factory is closer to the action, so it is rational to let the main shuck of forces move from here, against the main theater in Europe. But it is also a must to threaten Japan.
A strategy I am trying out now, is to buy all bombers turn 1 and 2, and let them either kill the german and italian navies, or SBR germany and italy. Then from turn 3 establish the usual shuck with inf/trannies against Africa or France or Norway.