How did the events of 1949 affect the U.S policy toward communism?

Overall, the events of 1949 contributed to a massive American commitment to contain and even roll back global communism. By 1949, the United States had committed to defend West Berlin from Soviet aggression, which it was still doing with the so-called "Berlin Airlift" in defiance of the Soviet blockade. American policymakers were alarmed by the victory of Mao Zedong's communist revolutionaries in China, which meant, from their perspective, that the most populous nation in the world had fallen to communism. They were equally concerned at the Soviet Union's successful detonation of an atomic bomb, which meant that the United States no longer had a monopoly on the world's most powerful weapon. The effects of these events (and the North Korean invasion of the South in the spring of 1950) were complex. First, the United States, in 1949, entered into a collective security arrangement with the nations of Western Europe, known as NATO (North Atlantic Treaty Organization). Second, the United States mobilized to contain the spread of communism through an enormous expansion of the defense budget. This course of action, recommended in a 1950 National Security Council memo entitled NSC-68, permanently shaped the American intelligence and defense apparatus. These events also sparked, or more accurately stoked, the fears of Americans that global Communism not only threatened to take over the planet, but to infiltrate the United States itself. The events of the year 1949 promoted the fear and hysteria among the American people often called the "Second Red Scare."