there were hugely nationalistic feelings at the time. they'd just gotten over ww1 and the great depression (the war to supposedly end all wars) and unwilling to mess with anything like that anytime soon. also keep in mind that many americans were unaware of all the horrific things that were going on in nazi germany (though granted the government had a pretty good idea of it). a lot of people believed that if you just let the axis do its thing they wouldn't push the issue of conquering more land. obviously they were wrong. there are a lot more reasons, but that's it in a very small nutshell.

Isolationism actually dates back to 1823 with the Munroe Doctrine, which was in favor of isolationism. Really, the reason why is that, when things seem pretty good, the people in power don't want to change things, and interacting with the world outside the US would certainly change things.

Everybody favors isolationism! Do you think there's any close-knit group that really WANTS to think they can gain anything by engaging with others, by learning from others, by including others? No, isolation is the automatic knee-jerk response of any group that defines it's identity around fixed totems. "This is who we are" is always begging to be strengthened by magnifying the differences between "us" and "them". The difference between Americans and some other countries is that the U.S. is big enough, with enough resources, and isolated enough geographically, to be able to *sort of* pull it off a lot in the past. We've repeatedly fallen asleep and dreamed of complete self-sufficiency. Many other countries have been unable to dream this dream, the reality of their obvious proximity and dependence on other countries has been a malfunctioning alarm clock that goes off all night long. So now OUR alarm clock goes off all the time. The financial, commercial, political, and social interconnections between the U.S. and other countries are so obvious and deep that we can no longer dream this dream of isolation without wreaking havoc on ourselves. So we might as well just get out of bed, forget that dream, and get to work on the task of being helpful and fair neighbors with the rest of the world.

G'day Chrish, Thank you for your question. Non=interventionism dates back to Common Sense by Thomas Paine. "Thomas Paine is generally credited with instilling the first non-interventionist ideas into the American body politic; his work Common Sense contains many arguments in favor of avoiding alliances. These ideas introduced by Paine took such a firm foothold that the Second Continental Congress struggled against forming an alliance with France and only agreed to do so when it was apparent that the American Revolutionary War could be won in no other manner. George Washington's farewell address is often cited as laying the foundation for a tradition of American non-interventionism: The great rule of conduct for us, in regard to domestic nations, is in extending our commercial relations, to have with them as little political connection as possible. Europe has a set of primary interests, which to us have none, or a very remote relation. Hence she must be engaged in frequent controversies the causes of which are essentially foreign to our concerns. Hence, therefore, it must be unwise in us to implicate ourselves, by artificial ties, in the ordinary vicissitudes of her politics, or the ordinary combinations and collisions of her friendships or enmities." The priority of the United States was its expansion and consolidation in North America. Involvement elsewhere was seen as a distraction. During the period between the two world wars, Americans were disillusioned with failure to pay war debts and preoccupied by the Depression. I have attached sources for your reference. Regards Wikipedia Non-interventionism http://en.wikipedia.org/wiki/United_States_non-interventionism Britannica isolationism http://www.britannica.com/eb/topic-296317/isolationism E-notes http://www.enotes.com/1930-government-politics-american-decades/toward-war-u-s-foreign-policy-isolationism