Lend Lease would only be extended to the Soviets at the point when it looks like Hitler might actually win. Lend Lease will be significantly delayed compared to OTL. Nobody will want to give any aide to the Soviets so they can conquer Europe. There's going to be several stages as to how the war is seen.
Stage 1, Initial Soviet Invasion - "Ha, we knew this would happen. Good to have Commies and Nazis killing themselves. Give neither of them aide."
Stage 2, German Defeat of the Soviet Invasion - "Excellent. The Red Army got a bloody nose, and now Hitler has a second front. This will help Britain."
Stage 3, Initial German Counterattack - "We knew this was going to happen. Weather is still good. I bet the Germans will make some limited progress."
Stage 4, the German Attack Continues deep into Soviet Union - "This is unexpected. Maybe we should start selling supplies to Stalin."
Stage 5, Germans drive towards Leningrad and Moscow - "This should not be happening. We want a prolonged Nazi-Soviet War that weakens both sides, not a German victory. What can we do to prevent this?"
At that point, and not before, will the US begin talking about providing aide to Moscow. I imagine there won't even be sales of materials to Moscow until sometime in stage 4 (which IOTL occurred from June to September 1941 before Lend Lease proper). And it will be much tougher to get it passed, and when Lend Lease is passed for the Soviets, it may come with all sorts of restrictions of what can't be provided. Furthermore, there may be demands that before any aide is given that Stalin repudiate all gains made during the MR Pact - that he'll free the Baltics, recognize Poland's eastern border, agree to surrender his annexations of Finnish and Romanian territory (even if he is at war with those countries as a result of his invasion.)
If Japan is at war with the Soviets, then that closes down the Pacific Route which IOTL handled 50% of all the traffic. Therefore any aid is going to take longer to reach the Soviets.
Also, the major reason the US passed the Oil Embargo on Japan in July 1941 was to discourage them from attacking the Soviets, not just in response to a move into southern Indochina. ITTL, things are so different that the US may not establish the oil embargo until quite later, delaying American entry into the war.
This will have a great impact on the Soviet war effort. It may drop them back anywhere from 6-12 months from OTL.