Any American aid to China will be offset by the extra resource's Japan can add to the fray, and without a war in Europe not even Japan is crazy enough to go on an offensively against the west.
Russia though... Japan might go for Russia. And if Russia is fighting a two fronted war she probably goes down in flames because the Persian corridor just can't handle the amount of Lend-Lease Russia needs to survive.
Sooner or later (probably later) Japan is going to get wore down from the endless fighting in China and America can hopefully try and negotiate some sort of settlement that lets Japan save face after so much spilled blood. A victorious Germany is a far, far greater threat to the free world than Japan could ever dream. So if America can pry Japan from German orbit it's a boon to the USA and a major blow to Germany.
Russia though... Japan might go for Russia. And if Russia is fighting a two fronted war she probably goes down in flames because the Persian corridor just can't handle the amount of Lend-Lease Russia needs to survive.
Sooner or later (probably later) Japan is going to get wore down from the endless fighting in China and America can hopefully try and negotiate some sort of settlement that lets Japan save face after so much spilled blood. A victorious Germany is a far, far greater threat to the free world than Japan could ever dream. So if America can pry Japan from German orbit it's a boon to the USA and a major blow to Germany.