How and why did the united states take a more active role in world affairs? give examples of how the united states became more active.

For many, the US's involvement in World affairs really shifted with World War II.

As America left World War II as one of two major superpowers (US & Soviet Union), it then became a race for strategic advantage in the world.

So, the United States got more involved in keeping the Soviet Union and it's representatives from spreading.

This led to incursions in Korea, Vietnam, and throughout Central America as part of the "Cold War"