Being the opponent of communism and the champion of freedom and democracy defined much of the US government's policies during the Cold War. There are many policies, both foreign and domestic, that you could examine. Let's look broadly at a couple of them here.

At home, there was a concerted effort not to allow anyone with even the slightest possibility of harboring communist sympathies to work in government. Numerous laws, orders, and programs were designed specifically to identify possible communist sympathizers and even possible foreign assets. President Truman established the Loyalty Review Board in 1947, and similar programs under all the Cold War administrations followed. This search for communists in government ranks sometimes got out of hand, such as with the witch hunts led by Senator McCarthy.

The focus of US foreign policy was to curtail communism. Perhaps the most prominent examples of this are the Truman Doctrine and the Marshall Plan. Under the Marshall Plan, the United States gave large amounts of money to war-ravaged Europe to rebuild and invest in infrastructure. Smaller foreign aid programs continued throughout the Cold War to build up friendly nations and their democratic governments. The Truman Doctrine was a promise of military intervention to prevent communism from spreading to new countries. At times, this got the country into wars, such as in Korea and Vietnam. President Truman called these two approaches "two halves of the same walnut."