Germans were crushed by and large by the USSR. If you look at number of troops fielded against Allies in Italy and France, and casualties, it's all really secondary to Stalingrad and Kursk.
Allied (mainly American) support in terms of supply was important to the Soviets in 1941-42, when their own industrial base was largely overrun and in shambles. By the end of the war, though, it was recovered to beyond its original (already very impressive) scale, and kept growing steadily. Look at the numbers of small arms, tanks and planes produced in the USSR in 1943-45, and compare to US and Germany; you'll be surprised. Certainly by 45, Soviets could get along just fine without lend lease.
It is a similar story with casualties. Most of that 1:2 disparity comes from the first two years of the war, when Soviets were getting steamrolled; the proportion then was actually far worse. But by 1944, it was already 1:1, and by 1945 the steamroller was in full reverse. Not surprising, given that purges in 1939-41 have decimated the Soviet officer corps, and it took a lot of bitter combat experience to grow the replacement - but by '44 it was there, lots of experienced, battle hardened commanders, and Stalin had put politruks on a leash, too.
So no, the USSR was not out of breath by '45. Quite the opposite, it had its war machine cranked out to full steam, and still considerable manpower resource with a lot of combat experience. Not enough to keep fighting an extended offensive for much longer, which is why Stalin stopped at Berlin. But certainly enough to stop any new invasion of its territory in its tracks.