Which of the following events was most important in moving the policies of the United States from isolationism to internationalism? a.) civil war b.) world war 2 c.) Vietnam war d.) terrorist attack of 9/11/2011

World War ll was the most important event that changed the United States from being isolationist to internationalist. Suddenly, we were propelled into world affairs after being isolated for more than a decade during the Great Depression. World War ll and the decades after changed how America dealt with foreign affairs and in essence we became a policing country trying to figure out everyone else's problems.