I'm not quite sure of the POD here, but the result is that by 1943, FDR's opinion on Stalin is almost exactly equal to Churchill's opinion on Stalin. Stalin still gets his invasion of Western Europe and the materiel (or at least most of it) that he got in OTL, but there are no illusions.
Any idea how the war is effected? My guess is that FDR and Churchill don't see the need for the Soviets to attack the Kwantung Army, but if the Kwantung Army is still in Manchuria (albeit with no way home), do the Japanese wait longer before surrendering?