American Exceptionalism is proving, as always, a very hard beast to put down. The belief that this country is not only unique in the world, but has a unique role to play in it is periodically turned out to pasture by some in both parties, and sooner or later finds its way in again. That's less because of its own perfections than because all other approaches are worse.

The idea began in 1904 when the Dominican Republic defaulted to on its debt to three countries in Europe and Theodore Roosevelt had quickly moved in, seized the customs house in Santo Domingo and settled the debts before the crisis could escalate. This was the first example of the preventive diplomacy he employed in his hemisphere and wished to extend to the world. Accepting the Nobel Peace Prize in 1910 after he brokered peace between Japan and Russia, Roosevelt used his acceptance speech to lobby the world on the need for such measures. "It would be a masterstroke if those great powers honestly bent on peace would form a League of Peace, not only to keep the peace among themselves, but to prevent, by force if necessary, its being broken by others," he said to his audience.

"The combination might at first be only to secure peace within certain definite limits ... but the ruler or statesman who should bring about such a combination would have earned his place in history ... and his title to the gratitude of all mankind." It was all wishful thinking, but in World War I he and his much younger fifth cousin Franklin would labor unstintingly to build the Anglo-American accord as the basis of this combination. In his own war years later, Franklin would create the Security Council in the United Nations, made up primarily of the five major countries that defeated the Axis, as the great combination cum global police force charged with putting down trouble before it could start.

Alas, two of those countries — Russia and China — began to emerge as the problem themselves, destroying the U.N. as a factor in anything, and forcing the West to outsource to NATO, which, forty years later, prevailed. In 1992 George H.W. Bush and Margaret Thatcher formed a coalition that drove Saddam Hussein from Kuwait, but since then a coherent response to the current malaise has eluded three presidents.

In 2011, Barack Obama got bored with it all and, after declaring Iraq a roaring success (in contrast to what he had said when the surge was in progress), pulled all the American troops out of that struggling country, allowing the worst elements from all over the region to pour into the vacuum that nature abhors. The results in 2014 were so catastrophic that they helped lead to a stunning rebuke in the upcoming midterms, a belated and frantic attempt to bring things back at least to the status quo ante, and a situation in Syria so appalling that Donald Trump was forced to lob a few missiles in that country's direction, while sounding like John McCain, Marco Rubio and, God help us, George W. Bush.

American exceptionalism revives when it has to, i.e., when its opposite has screwed up too badly, and the "police power" is called on to come in and clean up the damage the uncontrolled crime wave has caused. Roosevelt's search for the right "combination" to broker a peace is an ongoing quest, but no quest at all does not seem the answer. If we go on for a whole other century, is there a chance that we may get it right?

Noemie Emery, a Washington Examiner columnist, is a contributing editor to The Weekly Standard and author of "Great Expectations: The Troubled Lives of Political Families."