Though President Joe Biden called the United States military withdrawal from Afghanistan an "extraordinary success", most Americans are unconvinced.

Indeed, neither the US war in Afghanistan nor its ending was a success, let alone an extraordinary one. The last-minute loss of 13 US and many more Afghan lives and the lightning collapse of the US-supported Afghan government and the US-trained and equipped government forces in the face of the sweeping comeback of the Taliban capped a messy withdrawal. And the cost of the 20-year war was the loss of over 2,400 US and more than 240,000 Afghan lives, as well as the $2.26 trillion that Biden said the US has spent on Afghanistan.

The bloody images marking the finale of the "forever war" will dictate domestic politics for quite some time going forward. Of course, there will be more ferocious foreign policy debates. But amid the finger-pointing and second-guessing, there are lessons to be learned.

The US president shared some of what he had learned — that nation-building should not have been a US mission in Afghanistan and the war should have ended following the accomplishment of the initial anti-terror goals, and that he had wrongly assumed the Afghan security forces would be able to quell the Taliban resurgence.

In fairness to the sitting US president, he made a tactical mistake while attempting to correct a strategic one that had run through three consecutive US presidencies.

"This decision about Afghanistan is not just about Afghanistan. It's about ending an era of major military operations to remake other countries," he said.

Secretary of State Antony Blinken said now is the time for the US to reflect on the war and "learn its lessons and allow those lessons to shape how we think about fundamental questions of national security and foreign policy".

"A new chapter has begun — one in which we will lead with our diplomacy," he told Americans.

Hopefully that new chapter will show that Washington finally appreciates that war is not the answer to every problem, US values and institutional designs don't always work on alien soil, especially when they are imposed by force, and that there are limits to US capabilities and US foreign policies need adjusting to match a changing world.

The conditions in many parts of the world, from Afghanistan to Iraq to Libya to Syria, would have been quite different had the US not been so obsessed with intervening in their affairs.

Washington needs to accept the fact that history shows its use of power and military means to solve problems only causes more problems. As a linchpin of the contemporary international system, it should promote coordination, cooperation and dialogue, rather than careening around the world with what has become characteristic gung-ho impetuousness.