Answer:
The prominence of isolationism was subject to the most change as a result of President Roosevelt's Lend-Lease program.
Isolationism was a prominent ideology in the United States prior to World War II, and many Americans believed that the country should stay out of foreign conflicts. However, President Roosevelt believed that the United States needed to help its allies in the fight against Nazi Germany and other Axis powers. In 1941, he proposed the Lend-Lease program, which allowed the United States to provide military aid to its allies without actually joining the war.
The Lend-Lease program represented a significant shift away from isolationism and towards greater involvement in international affairs. It marked a turning point in U.S. foreign policy and paved the way for greater American involvement in World War II.