For the most part, trying to keep your own corner of the map from going to hell is the best you can do.
Isolationism wasn't compatible with the imperatives of the 20th Century, and I have a sneaking suspicion it has already obsolesced in the 21st.
Fascinating topic, especially since we have such a widely-spread user base here to talk about it, but I'm with Kat. Can we have a thread split. Keep the Assange/wikileaks stuff in the original and split the NATO stuff off?
I'm not isolationist, nor do I think that watching Hitler run over Europe would have been a good idea. My view is rather that the United States shouldn't hop into most conflicts, whether it is invited or not. It's not a matter of "we don't belong over there", it's a matter of how much we can afford to invest in fighting wars. Wars that don't provide economic or security benefits over and above the cost of the war should not be engaged in. Alliances in which the United States obtains the least benefit and the most burden should be dissolved.
Currently, there is precious little to recommend Europe, in the long term, to the U.S. It isn't a threat, and terrorist attacks against Europe cost us nothing. A major war with, say, Russia, might devastate Europe, but defending Europe or a European country against Russia or another foe would likely cost the United States more than simply watching from the sidelines. Japan is more useful as an ally, but the only potential threat to Japan is China, which is a more valuable trading partner than Japan.
Therefore, considering the costs versus the benefits to the United States, we are better off at this time pursuing a more "isolationist" policy. That doesn't mean that an isolationist position is always a good thing, just that at this time, any threat that the world would need the United States to combat would be a nation that the United States should probably allow to pursue its own aims.
Furthermore, the risk of such incidents is low. Europe is unlikely to be attacked by any power. While China is flexing its muscles, it is unlikely to pose a major threat to any neighbor anytime soon. This reinforces the benefits of removing ourselves from the obligations which we currently possess, and redirecting the time, money, and energy towards ourselves. We owe Europe and Asia no moral obligation to protect them, and we owe the Middle East no obligation to try to "save them from themselves" (as if we could). Nor can we "enforce" democratic governance (a contradiction in terms if there ever was one).