Forget Afghanistan. Let's nation-build at home first.

The assessment of the war in Afghanistan from the top US general there is grim. Without more troops, Stanley McChrystal warned in a report that was leaked recently, "The conflict will likely result in failure."

His candor should be applauded. It gives President Obama and the American public – nearly half of whom now oppose the war there – an opportunity to ask themselves how we are going to save Afghanistan when we have not figured out how to engage in successful nation-building at home.

There's no question we need it. Thirty percent of our students drop out before finishing high school. Our border with Mexico is awash in drugs and violence. Mexican and Russian mafias have strong criminal footholds in our cities.

Some of our Rust Belt cities have unemployment levels on par with third-world countries. Michigan, once America's industrial heart, is on government life support. California, once the country's dynamo, is near bankruptcy.

Taking on these tough challenges will require US leaders, both Democrat and Republican, to relinquish the idea they can remake much of the world in America's image and likeness.

Giving up that idea is hard to do in Washington, even for presidents. It requires them to defy powerful pressure.

Mr. Obama should recall that in 1962 President Kennedy instinctively resisted Defense and State Department pressure to send more troops to Vietnam. President Johnson was also wary of a troop buildup in Vietnam, but he fell prey to his own fears that Republicans would accuse him of being soft on communism if he flinched in the face of a festering Viet Cong insurgency.

America has a poor record of nation-building abroad. The George H.W. Bush administration and Clinton White House failed in Somalia. The most recent Bush administration bungled it in Iraq, where Iraqis continue to blow one another up now that Americans are increasingly out of reach as targets.

And now, bright as he is, Obama is showing us he learned next to nothing from the nine-year Soviet attempt at nation-building in Afghanistan that helped hasten the collapse of the Soviet Union.

Not long ago, a friend, a high Canadian government official, met with his Chinese government counterparts. The discussion turned to the subject of the United States. My Canadian friend told me that the Chinese delegate coolly observed, "We always expected the American empire to collapse, but we had no idea it would collapse so quickly."

The Pentagon and the US military command in Afghanistan now find themselves caught in a trap inadvertently set by their own politicians.

The US military speaks of winning the hearts and minds of Afghans when it's almost certainly the case that the Americans will always be seen as "infidel outsiders" occupying a Muslim country, just as the Russians were seen on the same real estate in the l980s.

Even if the Obama administration were to send half a million troops, the results would be little different. Just as the Communist Vietnamese enjoyed havens in Cambodia, Laos, and North Vietnam, so the Taliban and the rabidly anti-American Islamists in Afghanistan would enjoy similar sanctuaries in Pakistan and Iran.

Few US politicians have had the courage to tell the public that Afghanistan has a corrupt, tribal government, too weak to go it alone without US troops. Obama unwisely made Afghanistan his problem by escalating, rather than winding down, US involvement upon taking office. Now, the US is committed to policing it, creating a modern infrastructure out of a medieval society, while providing Afghans security and jobs.

How does this count as an intelligent investment when we are struggling to do the same thing here in the US? American political leaders have a moral obligation to repair their own republic before they try to reengineer Afghanistan. Nation-building at home will be at least as challenging as in Iraq or Afghanistan and far more important.

A prerequisite for this domestic ­nation-building is a spirit of goodwill with civil discourse that scorns rabid political posturing. Members of Congress must see themselves as colleagues, not enemies, and the public must not let buffoons with megaphones shape the debate at the expense of serious-minded observers.

No matter how great their material wealth, democratic nations cannot long survive, let alone mend themselves, without a spirit of public goodwill in the body politic. The run-up to the American Civil War demonstrated this.

Today, a similar ideological malice stalks the land. It is arguably more destructive than any Islamist terrorist threat spawned in Afghanistan. And this malevolent public rancor needs to be addressed with far greater urgency than Afghanistan, which is probably too broken to fix.

Walter Rodgers is a former senior international correspondent for CNN. He writes a biweekly column for the Monitor weekly print edition.