Lend-Lease shipments of food, TRUCKS, tanks and aircraft would have ended. The food and truck cancellations would have had the greatest impact. The Soviets focused on tank and artillery production as well as fighter and ground attack aircraft. They did not have a strategic bombing force. The integration of former German Army may have been problematic, especially of the Waffen SS units. I’d have to look up numbers, but I think in manpower, the Soviets may have had more men ‘in the line’ than the Brits, US & French. Thus Germans are an interesting factor. Also, we had destroyed much of the German rail infrastructure, thus would have had supply problems akin to what we had in the fall of 1944.
And as Capt Obvious said, the US and British populations were tired of war. Additionally the British were at the end of their replacements. And we still had to fight the Japanese. US forces were beginning to be transferred to the US for demobilization and/or transfer to the Pacific in April 1945.
The Russian army had just over double the troops in the field as we did. However, the German casualty inflected/received rate against the Russians was 3-1. The Russian army would have faired even worse against US troops with our complete dominance of the air. we also had full access to the northen German ports to deal with supply issues while the Red army would have to Truck everything in from Russia.