The above answer omits pointing out the reaction of Americans during the Cold War to the atheism of the Communist Bloc. Americans were frequently reminded of the atheistic nature of Communism and Marx's reference to religion as the "opiate of the masses." Several actions and events marked the American religious reaction to the Cold War threat:
- President Dwight Eisenhower promoted religion and church attendance as every American's patriotic duty. He commented in a speech:
Recognition of the Supreme Being is the first, most basic, expression of Americanism. Without God, there could be no American form of government nor an American way of life.
Eisenhower called himself "the most intensely religious man I know," although he did not join a church until 1953.
- J. Edgar Hoover, then Director of the FBI commented that parents did not give their children a choice about going to school; therefore they should not be given a choice about going to church. He admonished Americans that:
Since Communists are anti-God, encourage your child to be active in the church.
- Church membership and attendance and sales of Bibles increased sharply.
- Congress authorized the addition of the words "under God" to the Pledge of Allegiance to the Flag in 1954.
- Congress further authorized the addition of "In God We Trust" to all American coins and currency in 1955.
All of this was a response to and direct reaction to the perceived threat of "Godless communism," the great evil which many Americans believed was intent on destroying their way of life.
This a fantastic question, because when people discuss the Cold War, religion is not really mentioned as something important. But the truth of the matter is that one of the great differences between the two sides of the Cold War was religion and this played a huge role in the Cold War. Countries like the former Soviet Union, China, and North Korea were officially atheistic. They sought to stamp out religion in general and Christianity in particular. This fact played right into the hands of countries like America. There was a strong line of demarcation between the "godless" communist and the "god-fearing" non-communist nations. This was part of the psychological warfare on the part of the Western countries.
In light of all these point, astute historians have pointed out that Christianity, in part, lead to the demise of communism. Even in staunch communistic countries, they could never really stamp out Christianity. For example, the Russian Orthodox church remained strong, even if persecuted. The same can be stated in China, where there is an estimated 100,000,000 Christians today. I will add an excellent article on this topic; see the second link.