What nation did the US leaders fear was leading world wide communist movements in the red scare?

During the Red Scare, U.S. leaders primarily feared the Soviet Union as the nation leading worldwide communist movements. The Bolshevik Revolution of 1917 and the subsequent rise of the Communist Party in Russia heightened concerns about the spread of communism globally. This fear was fueled by events such as the Russian Civil War and the establishment of communist governments in various countries, prompting the U.S. to take measures to counter perceived communist threats at home and abroad.