Two words: Nuclear bombs. But, to claim that in 1945 the US (and Britain) couldn't conventionally bomb Russian cities is absurd. The B-29 could fly roughly 2,000 miles to a target at about 275 - 300 mph at 30,000 to 35,000 feet hauling about 8,000 - 12,000 lbs of bombs. The B-17 and 24 could carry about half that almost as far.
The Soviets really didn't even have any aircraft in 1945 capable of intercepting these aircraft easily. In the case of the B-29 there were as ill-off as the Japanese in high altitude interceptors.
On the ground the US was receiving in large numbers the M-26 and M-24 tanks. The Sherman was almost exclusively 76mm armed and HVAP shot (capable of allowing that gun to riddle a JS II at 500 yards) was also regularly available. The only advantage the Soviets would really possess was sheer numbers and those were on their last legs too.
With the US having vastly superior communications systems and fire controls for artillery the Soviets would have been on the receiving end of more than one TOT (Time On Target) barrage unlike anything they ever got from the Germans. The Western Allies would have walked all over them in armored combat. It is interesting to note that in the postwar world Soviet style armor using Soviet tactics and training never won a major tank engagement against a Western equipped and trained army.
It's a good thing for the Soviets that Patton didn't get his way.