America suffers a far worse economic double dip in the late 30s with the jobless rates climbing to near 30% before dropping back down. The GOP in the 38 election does much better and Americans in general become more isolationist then OTL.
FDR wins re-election by a very slim margin in 1940 and due to economic pressure and greater isolationist feelings he doesn't really start to put the sqeeze on Japan until early 1942. In June of that year Japan decides to attack the U.S. fleet. America enters the war against Japan, but no German DoW on the US yet because of the lack of Lend Lease aid to their enemies at that point in time. In August of 1942 the U.S. Congess passes Lend Lease and provides it to nations fighting the Axis and after several sea battles in the Atlantic Germany declares war on the US in December of 1942.
How damaging would such a delayed Lend Lease and U.S. enterence into the war be to the overall Allied war effort?
The US would be very well prepared for the war, as when the US passed the rearmament bill in 1940 they actually delayed arming in favor of Lend-Lease for the British and later Soviets, so it badly slowed US build up. In fact US stocks were raided, resold to companies, who in return resold it at a profit to the British. So not only was rearmament delayed, the US military sold off its inadequate stores to help the Allies. Without things like that then the US military is armed to the teeth in 1942 and it would be suicide for anyone, let along the Japanese, to attack the US. The would mean the British probably have to call it quits without LL, as they were pretty much out of foreign exchange by 1941. The Soviets would still be in the war and would get LL, but be further behind and probably much worse off without the British in the war passing on supplies to them from July on and the US from October.
When (if) the Japanese attack the US, which makes no sense if they've waited until nearly 1943, the Germans would not declare war, because the British have quit for lack of money, so the Germans would have their hands full fighting the Soviets and probably buying from the US.
The Japanese IMHO would attack on time in 1941, because they still think the US is getting ready to attack them, which, without LL, it will really look like it, because the US has not been giving away all of their rearmament arms. Instead of the US getting stronger by the day and the Japanese are terrified of waiting too long. Of course with the British dropping out of the war in early/mid 1941 due to lack of money, the Japanese can now trade with Europe, which in turn can trade with the rest of the world, enabling the Japanese to avoid the US blockade. Transshipments that is. So the US not offering LL would mean the US probably doesn't enter the war at all, as the British would bow out and the Japanese don't need to worry about attacking anyone in Asia but China, as the European Axis can now help the Japanese circumvent the blockade. Also the British would do everything they could to placate the Japanese once they have run out of money and realize that fighting yet again, this time in Asia, is too much for their treasury. But without the blockade biting as hard, the Japanese keep focusing on China and Britain doesn't matter to the Japanese, who need every man fighting in China, instead of a Pacific campaign sideshow.
