U.S. + British + France GDP was 7 times bigger than Russia at end of the war. Western allied air supremacy ( including a nuclear monopoly ) would have obliterated Soviet logistics.
The West had the upper hand and Stalin knew it.
I wonder if those GDP numbers capture everything relevant to military advantage. The USSR produced as many tanks in a year and a half as Britain did throughout the whole war, despite having the same GDP.
Certainly it is true that with the nuclear monopoly the US had the upper hand; what we're discussing here is what Stalin would have believed if the bomb had remained secret, or perhaps only been demonstrated on uninhabited Pacific atolls, so the nuclear monopoly would not have figured into his calculations, or been a more theoretical factor. Or, more precisely, what Truman believed Stalin would have believed.