Bombed Pearl Harbor
FDR froze Japanese assets and established an embargo on oil and gasoline exports to Japan which led to the Japanese attack. Not isolationism.
In your isolationist utopia in WW2, we would have never stopped selling the Japanese oil and would not have fought them.
Would the world have been a better place? No
Responding to Japanese occupation of key airfields in Indochina (July 24) after an agreement between Japan and Vichy France, the U.S. froze Japanese assets on July 26, 1941, and on August 1, it established an embargo on oil and gasoline exports to Japan.