In this scenario I think a lot would depend on what happens in the east. Not so much the west.
The Americans had the nuke, had the pacific on lockdown and had the capability to strategically bomb and invade a superpower via the pacific alone. With Japan broken or at peace with the allies, this mean a us invasion of mainland Asia could have been conducted.
Mind you, there wasn�t much to invade in the Soviet Far East., but all the same. Russia would be fighting a two front war with no lend lease as mentioned, against a swath of allied nations.
I doubt they’re would be a reason to land in China, US wanted to liberate China but the ROC couldn’t secure a deep water port. So if US had to land invade USSR from the east, they would have to bypass Japan and most likely would take out Japan first or go into USSR east thus forcing the USN to destroy the Red Pacific Fleet.
Depending on when the West decides to take on the Soviets, destroying the Red Pacific Fleet might have consisted of sinking ships the US had sent to Russia: https://en.wikipedia.org/wiki/Project_Hula (“Project Hula was a program of World War II in which the United States transferred naval vessels to the Soviet Union in anticipation of the Soviets eventually joining the war against Japan, specifically in preparation for planned Soviet invasions of southern Sakhalin and the Kuril islands. Based at Cold Bay in the Territory of Alaska, the project was active during the spring and summer of 1945. It was the largest and most ambitious transfer program of World War II.”)