Final answer:
The link between events in the Soviet Union and discoveries in America can be considered the main reason for the development of McCarthyism.
Step-by-step explanation:
McCarthyism, the anti-communist movement in the United States in the 1950s, was influenced by the events happening in the Soviet Union and discoveries in America. The fear of communism was heightened by the victory of the Communist forces in China, the outbreak of the Korean War, and the political climate of the time. These events led to a growing concern among Americans about the threat of communism and resulted in McCarthy's accusations and the development of McCarthyism.