Answer:
US foreign policy began to directly intervene in Southeast Asia to restrict communist military insurgents.
Explanation:
The excerpt within the speech is now known as the "domino theory." This is the idea that if one country fell to communism, neighboring countries would also fall to communism. This fear of communism spreading caused the American federal government to adopt the policy of containment. Containment is focused on stopping the spread of communism.
This is why the US will intervene in different Southeast Asian countries like Korea and Vietnam. America fought in both these wars in hopes of stopping the spread of communism within this region.