Soviet Union Attacking a NUCLEAR UNITED STATES? The United States hits the Soviet Union for 50 Million, Game Over.
More to the point, the end of World War Two was really a bitter ending--a war fought to liberate Poland and Czechloslovkia that achieved neither.
I would argue that Stalin was given more of Europe than he should have been allowed. If you consider, as I do, that the Soviet Union and Nazi Germany will not agree to a peace deal at all between them, no matter what, the logical direction is that the ideal outcome of WW2 is that the United States needs to ensure that it alone wins. The ideal endgame for WW2 is something like Germany loses, the Soviet Union loses and Japan loses.
So, by giving the Soviets less aid the United States can get more of Europe. Would the Germans kill more Americans? Maybe--but their military situation was hopeless after D-Day OTL, and would probably be little better even in this scenario. Germany has no answers to an American nuclear weapon, either, so its hard to say that the USA will fare that badly for the lack of help of the Soviet Union.
And if the Soviets want to play tough, they can enjoy the taste of Sunny D, courtesy of the US Air Force.