As everyone is pointing out this is not helping the Japanese.
However, it is decidedly not helping the Soviets either.
It is hurting the Soviets, most significantly, by cutting off Far Eastern Lend-Lease.
However, the impact of this, I believe, is too long term to have major decisive operational effects on the Barbarossa campaign of 1941. Stalin will give Europe, which is far more valuable than the Far East, first call on all reinforcements and resources from the interior of the country, even if that means leaving the Far East forces to fend for themselves.
The first people to suffer in the Soviet Union from lack of Pacific Far East Lend-Lease will be Soviet prisoners, the small numbers of Axis prisoners, and Soviet civilians starving. But front lines in Leningrad, Moscow and the Volga won't falter.
The point of maximum danger from lack of Lend-Lease will come in summer 1942. Even here, Stalin will prioritize Europe above all else, but more choked supply lines will hurt more this year.
I'm inclined to think the USSR will make it through '42. The cost of the extra front I feel will be more long-term for the Soviets as they are more fatigued, more stretched, less mobile and therefore have a somewhat weaker and slower pursuit against the Germans after alt-Stalingrad.
But, the Japanese are also getting absolutely worn down and doing a lot less damage to China and the west, so the west is doing more on both fronts, really from the beginning of 1942 on, at an ever accumulating rate.