It's really no surprise that the United States has, throughout its history, held the concepts of isolationism and non-interventionism in such high esteem. The last sixty-five years are anomalous in terms of the greater sweep of history - the United States became active in the world at large in 1945 to prevent Allied victory from being swept away, and has remained active since 1991 out of inertia and self-interest. Nevertheless, the world has changed substantially in the last twenty years, and as time goes by it seems more and more believable that the world's policeman might hang up his badge.
The concept of American non-interventionism stretches back to before the Revolutionary War, though perhaps its most significant signal boost was made by Thomas Jefferson in 1801, when he called for "peace, commerce, and honest friendship with all nations, entangling alliances with none." At the dawn of the nineteenth century, that was an eminently practicable philosophy. The young United States had all the resources and dynamism of a pioneer society and was poised to explode west over the Appalachians. National self-sufficiency was far simpler to manage, as the Industrial Revolution had yet to start chugging on when Jefferson took office, and the wide borderlands and vast seas gave the United States all the defense it needed.
Things have changed a bit in the last two hundred years. Thomas Jefferson never had to worry about pandemics or ICBMs or environmental disasters. But that hasn't dislodged the concepts of non-interventionism and isolationism from what seems to be a uniquely privileged place in the American world of the mind. I, personally, can't think of any country, except for Imperial China, that thought that way.
But it's not dead, IN AMERICA! Rand Paul, son of lolbertarian-favorite 2008 presidential candidate Ron Paul, is reportedly now the man to beat in today's Kentucky Senate primary. On his website he cites Jefferson's address and suggests that "allegiance to foreign institutions sacrifices our autonomy as a nation by transferring our legal authority to unelected and unaccountable leaders." Personally, if that's the case, my answer would be that the problem is with how those institutions are organized, not with the institutions in and of themselves.
The twenty-first century has created a world in which distance is no defense; the Atlantic and Pacific may as well be puddles for all they can prevent enemies reaching North America's shores. Nor do we live in a world where countries can rely on none but themselves. Take titanium, for example: during the Cold War it was an absolutely vital for advanced aerospace construction, and the United States needed as much of it as it could get.
We're also living in a world of grander problems than those Jefferson had to deal with. Take your pick from nuclear non-proliferation, environmental remediation, international stability, global patent and intellectual property regimes, or any of dozens of other issues that cross borders as freely as the air. Modern-day problems are of global scope, and while we live in a world where collaboration across countries and continents is becoming easier, it's also becoming more and more necessary.
The future is potentially bright, but the world has grown into a state of such complexity that no one state has the resources to chart a course through the rocks and shoals on its own. The age of being "in the world, but not of it" has, I think, passed forever. Cooperation and coordination is what will let us realize the best of the futures.