Russia certainly would have beaten Germany without the US, but that actually may be the problem. If they had won by themselves, they would have kept on pushing into Europe, and the Iron Curtain would have been further west. Of course, the world is far too complex to really make reliable predictions about a different history, if such a concept can even exist. I'd say the US's greatest contribution was actually in helping to rebuild Europe and Japan. The money itself may not have been huge, but the Marshall Plan was very successful because it forced economic reforms and European integration (like the Coal and Steel Community) that was the precursor of the EU.
Regardless, it's ridiculous to have some kind of national "debt" of gratitude in the first place, but even more so since the actions were purely pragmatic, not out of some great generosity.
Regardless, it's ridiculous to have some kind of national "debt" of gratitude in the first place, but even more so since the actions were purely pragmatic, not out of some great generosity.