We can all hope that it will be a long, long time before the United States is again tempted to invade another country and then face the redoubtable task of rebuilding it, politically as well as physically. If that day ever comes, though, the American experience in Iraq will offer an object lesson in how not to do it.

The United States has spent $60 billion to reconstruct Iraq and, according to a new report, neither country has much to show for it. It wasn’t a complete waste, since our invasion of that country compelled us to stand it up again, but no one got our money’s worth. Much of the reason for that appears to be because American leaders were unwilling to listen to Iraqis about the projects that would make a difference.

The report to Congress is the last one expected from Stuart Bowen, special inspector general for Iraq reconstruction, and it is unsparing. He said at least $9 billion of the money was lost to poor planning and weak oversight that allowed waste and fraud to permeate the effort.

The project may have been snake-bitten from the start, given the large role given to the Army, whose job is to wage war, not build countries. American leaders also failed to involve Iraqis in decision-making about construction projects, thus giving them little psychological investment in the work undertaken. Many projects are incomplete or in shambles from neglect.

The entire cost of the Iraq War to the United States is a matter of dispute, but estimates range from $845 billion to $3 trillion – enough to wipe out the federal budget deficits of the last three years and to have made the enormous costs of the Great Recession significantly more manageable. While both Presidents Bush and Obama share responsibility for those costs – especially Bush – it is worth keeping those costs in mind as Americans consider the sources of those deficits.

Some of these lessons may be applied, if belatedly, to the wind-down of the war in Afghanistan. There, Americans have spent $90 billion on reconstruction projects, and there could be similar problems there without better planning.

Americans have been in Iraq for 10 years and in Afghanistan for more than 11. It is past time to leave. Although neither country is as stable as it should be, given the vast amounts of blood and treasure expended there, there is little reason to believe that anything would change if we stay longer and raise those costs still higher.

But it is worse than a shame that this country launched those invasions while giving too little thought to the important task of reviving those countries once we knocked them down. If there is ever a next time, presidents and generals and members of Congress need to learn critical lessons from this time.