@ABWorsham:
How would the war have changed had Pacific Lend Lease convoys needed heavy protection, carriers, battleships and destroyers?
Had the Germans held the Stalingrad and Caucasus Mountains, they could have harassed any supplies routes east of the Caspian Sea.
From my readings on the subject the Red Army and Lend Lease materials, the addition of 300,000 heavy trucks and 400,000 jeeps had the largest impact on the war in the East. The Red Army also loved the P-39. Five out of the 10 highest scoring Soviets aces logged the majority of their kills in P-39s.
Germany was not prepared for a war of such immense scale with the Soviet Union.
If you combine cutting the lend lease with other factors like shifting Germany’s industrial output to total war much earlier, then there might have been a chance of military success. But, as long as the Russians had a production, manpower and logistical advantages I don’t really see how they could have won.