The answer is, depending on the conflict and relation with other nations. It also depends upon resources from other countries. The Soviet Union and Cuba did not survive isolationist policies, the same happened with Spain under Franco, who eventually was related to Nazi Germany and Fascist Italy. Historically, nearly all ancient civilizations, kingdoms and city-states engaged in foreign/international trade. In recent history, isolationist policies tended to be connected to nationalist movements, these policies do not last.
Before WWII, United States demonstrate its isolationist policy by avoiding alliances and other international relationships. One of the causes for that behavior was the U.S. intervention in WWI and the large number of American casualties during that war and the economy devastation.
With this reasoning it is understandable that in order to avoid casualties the U.S. chose to not get involved in foreign conflicts.