Answer. Not very easily by any stretch of the imagination post 1900. It would involve A LOT going wrong for the West and A LOT going right for the USSR. I don't actually think a "defeat" of the USA in the Cold War is even possible ala the US collapsing as the USSR did because it was simply a nation with better leadership, better industry, better technology, a more educated population and a very advanced military. It was on the better side of World War II, enjoyed technological supremacy and access to much of world's resources. Honestly, in order for this to happen, the US needs to be led by much weaker men who only make stupid decisions. The USSR is still going to be plagued by the issues of unemployment, a draconian government and a very depressed population, who for years had felt they had simply traded one horrible dictatorship for another.