AFAIK, their war lay primarily in the Pacific, and beyond supporting the Brits and Russians materially, I’m not really sure why the US would want to involve themselves physically in the European theatre. I do feel fear of Germans beating them to the bomb might have something to do with it, but that’s just conjecture.
Is this a serious answer?
The whole reason they gave Czechoslovakia to Nazi Germany and Poland was to give them a clear path towards invading the USSR.
Stalin’s diplomats engineered the Molotov-Ribbentrop pact at the last minute to drive a wedge between Germany and Poland, forcing the Nazi Germany invasion of Poland, and the Brits and the French to respond in kind.
The Brits already signed the Dusseldorf Agreement just a few months before Germany invaded Poland, which encompassed industrial cooperation between German and British industries. They fully expected Nazi Germany to take the USSR out, and the forging of close economic ties with Germany down the road.
The fact that Hilter turned against them was a genuine surprise (most of the Western imperialist powers refused Stalin’s plea to form a coalition against the rise of Nazism in Germany, and in fact most of them already signed military and economic cooperation pacts with Germany since).
The US definitely did not want Stalin to take over the whole of Europe.