In my view, the US president that produced the most vital and most crucial cold war policies was Harry S Truman, who was president from 1945-1953. A large part of his presidency was focused on foreign policy and the Cold war, such as the Containment policy, which was a plan to limit the spread of communism by creating a European economic recovery program (Marshall aid) and the Truman doctrine, 1947 to get Europe out of poverty and to protect these countries because the USA had started to realize that the interests of the USA and the USSR were becoming incompatible. The containment policy is one of great importance because it created many rival policies from the USSR because they viewed the USA's actions as their wish to expand their sphere of influence and dominate the world.
The Berlin blockade of 1948-1949 saw Truman forming another important cold war policy which was the creation of NATO in 1949 to provide a common defense for the USA and her allies against the soviets, this was a shift from normal US foreign policy because this was the first peace-time military alliance the USA had ever joined.
These policies to fight communism led the USA into Vietnam to try and contain it and prevent it from spreading because the USA was afraid of the 'Domino effect' that if one country falls to communism the same will happen in nearby countries. Although he wanted to stop communism by all means Truman was also a great backer of the establishment of the United Nations, which sought to settle matters in a peaceful manner
The policies of Truman were all to try and prevent the spread of communism and these formed the most vital part, sort of like the backbone of American cold war...