After the defeat of Germany and Japan, the US war machine was fully ramped up. In 1944 the US built over 96,000 aircraft with 74,000
+ combat aircraft. In 1945 with the war winding down we built almost 46,000 with almost 36,000 combat aircraft from January to August. Similarly, almost 18,000 tanks and sp guns in '44 and about 12,000 in '45.
Had a war against the Soviets happened, the entirety of US production would have been focused on them. It also could easily have been a 2 front war, one front in Europe another in Asia using Japan as the base against the Soviet Far East.
I don't think they could have matched the US supply of war materials nor the logistics capabilities of the US.
Bloody, costly...yes. Don't think the Russians could have won it though unless the US politicians had fought it like they fought North Korea.