ORIGINAL: Twotribes
No telling when the US would have acted with out a Japanese Attack. Roosevelt wanted us in but didnt feel he had the needed votes to do it, so he skirted the issue by doing other things to help.
I suspect that a Japanese attack on GB and the NEI would have put the number of votes in Congress for the war over the top--if not it would have moved things a lot closer. Even with no Japanese attack at all the US would have declared war on Germany within six months.
Most War games have the US join in December 41 or January 42 even if the Japanese dont attack. Just an artifice, just like if the Germans dont attack the Soviet Union in 41, most games have her able to do so on her own shortly there after.
World in Flames has a US entry track--every time Axis or Allied players take certain actions, US entry can be moved up or moved back. In early editions this resulted in highly ahistorical games, as the Allies would avoid nearly every action that had the potential to reduce US entry (lend lease, neutrality patrols, Japanese oil embargo, etc.), and the US generally entered the war early in 1941. In later versions of the game this was corrected somewhat, by making US entry a dice roll which becomes more likely as the US picks more entry options (which tend to reduce the US-entry index) in addition to being tied to the entry index. As a friend of mine put it, "We don't just have to get mad at the Axis; we also have to get ready." The US player can try to roll as soon as he has a chance greater than zero, but if he doens't make it, US entry is reduced, and other bad effects happen (simulates FDR asking for a DoW but not getting it).
BTW, in the early editions of WiF if Japan declared war on the Netherlands or GB, the US was allowed to declare war immediately. In the revised US-entry system, war isn't automatic, but the chances go way up.
