I know I'll get alot of flak on this, but anyway, here goes. 
I really like the game. I'm jealous--I wish I'd developed it. I've gotten some ideas in my head to "tweak" it.
One is that the US doesn't increase it's production capability automatically when it goes to war, but incrementally, especially if it goes to a war footing. To wit:
1939 and 1940--USA gets 4 production points/turn
1941--USA gets 12 p. p./turn (starting with the Dec. 1940 turn)
1942--USA gets 40 pp/turn
1943--USA gets 80 pp/turn
1944+--USA gets 115 pp/turn
I suggest this as my research shows that the USA took some time to develop the manufacturing facilities and proceedures over several months and it did not happen automatically. In terms of the GNP and Defense spending over those years, I think this is a good progression. Of course, the USA is an economic powerhouse, but not at first. The "Arsenal of Democracy" will take some time to develop. It will change the game's play. Anybody got some other thoughts?
I’m not out to give you the “flack” you’re talking about, but I see some real issues with this suggestion.
To begin with, it would dramatically impact game balance. From the games I’ve played, the Axis is usually getting to around 30-35 victory points when the US enters the war (assuming entry +/- 1 turn from historical). At this point the Axis has to begin to divert resources to defend what they’ve taken in order to fend off the US, who can usually begin to create some real threats after a couple of turns of building with a war economy. About the time the victory point total needed for Axis victory begins to drop, the Allies (thanks to US production) are able go on the offensive enough to challenge the Axis being able to achieve the victory total. The game seems very balanced as it is, with both sides having a decent shot at victory on points. With what you’re proposing, given competent (or even just close to competent) Axis play, I see no way for the Allies to prevent the Axis from winning the game on points.
Also, your proposal doesn’t take into account that the US was already gearing up for war before Pearl Harbor. The North Carolina and South Dakota Classes were already undergoing sea trials at the start of the war, and were operational by the start of summer 1942. Essex Class CV’s and Iowa Class BB’s were already on the slipways. Aircraft production ramped up to where the US could begin serious strategic bombing in Germany by 1943. Keep in mind also – the US didn’t just build things for itself – it was also shipping military hardware to Britain, China, and the USSR while simultaneously building up its own war effort.
As to the US not being an economic powerhouse at first – well, that sort of means what you mean by “economic powerhouse.” True, the US economy before the war wasn’t what it would be by the time the war ended (at which time it was still only really getting warmed up – the US cancelled production of a lot of military hardware well before the war ended, simply because they knew they weren’t going to need it), but even before the US entered the war, its “war” production compared very favorably with what the Axis powers managed to do while they were in the war.
The US built over 25,000 aircraft and over a million tons of merchant shipping in 1941 alone; for the year 1942 the US built more merchant shipping tonnage (over 5 million tons) than Japan built for the entire period 1939-45 (4.1 million tons). Total US aircraft production 1939-41 was nearly 45,000; this is nearly two-thirds what Japan produced 1939-45. In 1942, with 47,836 aircraft built, the US more than doubled total aircraft production of the previous 3 years combined In 1941, the US built over 4,000 tanks and 5,000 halftracks; as a comparison, some sources (including Jane’s) report that Germany built less than 5000 Pz IV’s of all models during the entire war.
In the US’s first year at war, 1942, they commissioned 18 aircraft carriers (of all types), 4 battleships, 8 cruisers, 82 destroyers, and 34 subs. This compares very favorably to Japan’s totals of 17 aircraft carriers (of all types), 2 battleships, 9 cruisers, 63 destroyers, and 167 subs –except that the US total is only for 1942, and Japan’s total is for the entire period 1941-45.
My point is, with your proposal, the US can’t build at the levels that they did historically, either before or after they enter the war.
I have to also say I can’t imagine you’d find anyone willing to play the US player using the rules you propose.
If you really want to experiment with requiring the US to have more of a “gear up”, as you call it, I’d suggest trying one of the following (assumes you are using event-driven US entry):
1) US does not get additional production points for factories built until they are at war.
2) Same as above, with the addition that each turn after at war one factory on the map “comes on line” and contributes its 5 points to US economy.
3) Require the US to supply 5 PP of Lend Lease per turn until Tension Level 1, and 10 PP per turn after Level 1 until at war.
4) Use a bid process to determine who plays the Allies, in which each player bids a number of turns that he is willing to play the Allies with no US production. For example, Player One bids 1 turn and Player 2 bids 2 turns. In this case, Player 2 will be the Allied player, and will not have a US turn for the first 2 turns of the game.
5) Alternatively, if you want to adjust the economics to give the Axis a break, use a procedure as 3) above, but bid on a number of PP’s that the Axis starts with “in the bank”. Player 1 bids 8 points for the Axis, player 2 bids 10 points. Player 1 wins, and will have 8 PP’s “saved” from a theoretical Summer 1939 turn, and thus available to be spent on the first turn in addition to normal income. These PP’s can be allocated between the three Axis powers any way Player 1 sees fit.
