There were a number of key interventions that the US took in Europe and in the Third World over the course of the Cold War. The most important interventions in Europe came early in the Cold War while interventions in the Third World were more spread out over the entire period of the conflict.
Right after WWII, the US intervened in Europe to help prevent the spread of communism. Perhaps the most important of these interventions was the Marshall Plan. This program gave billions of dollars of aid to Western European countries to rebuild their economies. It was hoped that this would make them less likely to become communist and more likely to side with the US. Another famous intervention was the Berlin Airlift. Here, the US (with help from Britain) flew tons of supplies into West Berlin every day to prevent it from falling to communist pressure.
Interventions in the Third World occurred over much of the Cold War. For example, in 1950 the US intervened in the Korean War. South Korea was, in those days, a Third World country. The US was still intervening in the Third World in 1964 when it truly took over the war in Vietnam. It was still intervening in the Third World at the end of the Cold War when the US was trying to arm the Contra rebels in their fight against the Sandinista government of Nicaragua.
All of these can be seen as key interventions taken by the US during the Cold War.