Question

In the early 1940s, the United States was determined to prove to the world that her motives for entering World War II were:

Answer 1

In the early 1940s, the United States was determined to prove to the world that her motives for entering World War II were "to re-establish peace in the world," since most of the US was isolationist at this time. 

Answer 2

to re-establish peace in the world