Which United States action resulted in the end of isolationist foreign policies?

Question

A.
the United States’ entry into World War II
B.
the United States’ entry into World War I
C.
the United States’ invasion of Vietnam
D.
the United States’ annexation of Hawaii

Answer 1

A. the United States’ entry into World War II

The United States' entry into World War II is often seen as the action that marked the end of isolationist foreign policies. Prior to the war, the U.S. largely adhered to a policy of isolationism, avoiding involvement in international conflicts. However, after the attack on Pearl Harbor in December 1941, the U.S. entered the war and took a more active role in global affairs.