Question

Why did the United States join the North Atlantic Treaty Organization in 1949?

to improve relations with communist countries in Eastern Europe
to protect against the Soviet Union and the spread of communism
to share a common currency across all nations within the treaty
to create a policy of using military force to combat terrorism

Answer 1

to protect against the Soviet Union and the spread of communism

Explanation: After World War II the United States and Western European countries formed NATO (1949) as a collective defense alliance (Article 5) to deter Soviet expansion and contain communism, not to improve ties with Eastern Europe, create a shared currency, or focus on combating terrorism.