Why were many Americans interested in remaining isolationist?

The short answer: Americans felt that they had to focus on their own problems (economic, etc.) back at home rather than deal with other countries' conflicts.

The long answer: The results of World War I were drastically horrible, with thousands of soldiers dead and hundreds of civilians killed in America alone. Not only that, the country soon fell into the Great Depression - - which left Americans feeling more hopeless than ever. Not only did they NOT want to repeat history (the trauma of the First War was too much to bear), but the economy was in peril and Americans were struggling to feed their families and find jobs. Do you really think that hearing that there's this huge conflict going on overseas, that Americans are going to want to take ANY part in at first? No, not all. No way. Most Americans just didn't feel it was right to get involved in a foreign conflict when your country is dealing with enough issues at the moment.