Have Roosevelt take a Japan first policy. Stalin gets angry and threatens to sign a seperate peace with Germany, but Stalin is either bluffing or the Germans reject any offer because of Hitler. Relations get strained with the West either way. The extent of Soviet spies infiltration get discovered in the US, and relations further deteriorate. All US trust in the Soviets is removed. Roosevelt ultimately removes Lend Lease in early 44, as he believes the Soviets are no longer needed and allowing them to advance too far is dangerous.
Militarily, the Germans do much better against the Soviets in 42, capturing Leningrad and avoiding total disaster at Stalingrad.
The US and Britain launch a failed invasion of France in 43 while largely ignoring Italy, failing to take any pressure off the Soviets through land fronts in Europe.
In early 44, the Soviets are still on the defensive in Europe. Italy falls to Western invasion in the Spring and Greece in the early Sumner. Japan surrenders unconditionally in the early fall and Manchuria is handed over to the Nationalists. The Soviets begin to finally make major push backs against the Germans in the fall, but exhaustion and Winter slow them down.
In Spring 45 the Western allies take Northern France and secure Bulgaria defection to their side. By early Summer the Soviets are still struggling through Western Ukraine and Belarus while the West secures all of France, the Low Countries, and gets Romania to surrender to the West. During the mid Summer the West makes it into Austria and Germany while the Soviets make it to the prewar Polish border. Hungary gets invaded.
By the end of August, Germany gets nuked twice outside Berlin and surrenders unconditionally with Western forces in Prague and Budapest. The German forces in Poland surrender to the West and Polish rebels.
Postwar, the Soviets keep their 1939 gains at the expense of Poland and Finland along with the annexation of the Baltic trio. Even Bessarabia gets away. Not a single Uropean satellite state for te Skviets. China and Korea also escape their influence. The Soviets also have to deal with an extra 4 million dead due to famine without lend lease in the last year and a half, millions more civilians mursred by the Germans, nearly ten million extra military killed and crippled, and far more war on their own soil damaging their infrastructure.
The Soviets just aren't very intimidating post war here. Britain, France, Germany, Japan, and China all have bigger economies within 25 years. The entirety of Europe is anti-Soviet and begins developing post war. An economic community in Europe along with military alliances and UN membership are fostered to preserve peace, and the Soviets (who were pretty much broken and bleed white by 45 here) can't do anything to intimidate the alliance overall.
The Soviet's don't get the bomb until the early 50s here after their spies have been caught, giving the US a huge leg up. By the time the Soviet's get the bomb Europe is rebuilt on net (still behind in many ways but ahead in others) and firmly committed to the US. By the time the Soviets have enough bombs to poss a serious threat Europe, China, Japan, and united Korea are economically surging with Britain, France and China having their own nukes. By 1965 it becomes debately whether the Soviets are even capable of beating China in a one on one conventional war. Even without most of Europe heavily militarized the combined conventional strength of the rest of the continent exceeds the Soviets by the 60s. America doesn't even keep much of a presence in Europe by the 60s here.
No Korean or Vietnam wars happen. Castro dies and Cuba uneventfully becomes a a Democratic Capitalist state. Communists are largely locked out of every region here without Chinese, Cuban, Eastern European, or other infamous regimes backing.
India also somehow has the right people fall down staircases so that Liscence Raj is avoided and they begin developing sooner. Brazil likewise does better here with more competent strongmen.
No oil shock crisis happens.
There is still rivalry post war between the US/West vs Soviets/Communists, but no major flash points ever pop up and the Soviets are generally viewed as outright weak compared to the West and its alliance bloc. To the point that the Soviets are not generally taken seriously by the public at large. By the 70s China is a bigger power, and India, Japan, Britain, France, and Germany are not far off while Italy and Brazil aren't really that far off.
The Soviet Union goes bankrupt over a decade earlier here and collapses spectacularly again. It goes down as a more short lived, unimpressive country without much memory in the American mind.