I'm often asked by people outside America to explain US foreign policy. It's a daunting task or, perhaps more accurately, an embarrassing one. Americans know very little about the world. Their ignorance is almost charming.
In one sense, it's good that most people are more interested in spending time with family and friends than in waging a war against an emerging power or issuing foreign ultimatums. But, as an unfortunate result, Americans have essentially delegated the power to do all those things to a Washington-centred elite. When things go wrong, Americans get angry and policies sometimes change. But Washington's interventionist enthusiasm always quickly returns.
It's not a pretty spectacle. Most Americans are not ideologically committed to turning the US into an imperial power. Few of them would like to spend months or years patrolling failed foreign states like Iraq. Most of them turn against needless conflicts when it becomes evident that they aren't going to be short and sweet.
Anger over the Bush administration's Iraq war led voters to transfer control of Congress to the Democrats. Congress' failure to override the president may lead voters to give the White House to the Democrats as well.
Yet, in a perverse sense, the biggest foreign-policy problem is when the costs seem low. Then, the public simply ignores the issue, giving policymakers wide discretion to continue advancing interventionist policies contrary to America's national interests.
How else to explain continuing American membership in Nato, especially a Nato that keeps expanding? Europe once needed defending from the Soviet Union. From whom is the United States today defending Europe - a continent with a population and gross domestic product larger than America's?
Similarly misguided is America's continuing defence of South Korea. The South has more than 40 times the GDP and twice the population of North Korea. Most South Koreans no longer fear Pyongyang; in fact, they have been subsidising North Korea for years. Then there's Japan. The second-ranking economic power on Earth, Japan could do far more to protect itself and its region.