While America was consumed this summer with quarrels over town-hall radicals, “death panels,” the “public option” and racism’s role in the plunging polls of Barack, what happens to health care is not going to change the history of the world.

What happens in Afghanistan might.

Gen. Stanley McChrystal has done his duty. He has bluntly told his commander in chief what he must have in added combat troops and warned that if he does not get them, America faces “mission failure.”

Translation: a Taliban victory and U.S. defeat, as in Saigon 1975.

Not only does President Obama face the most critical decision of his young presidency, this country is facing a moment of truth. Obama, now the Decider, has four options.

There is the Biden option of drawing down troops, drawing away from Hamid Karzai, and focusing McChrystal’s men on what they do best—running down and killing al-Qaida, be they in Afghanistan or Pakistan.

Second is the option of indecision—holding off on more troops until the 68,000 already committed have arrived by December, and seeing how McChrystal does with them until spring.

The third option is to give McChrystal some but not all the tens of thousands he says he needs.

Final option: Give Gen. McChrystal the blank check George W. Bush gave Gen. David Petraeus, with the surge of 2007 in Iraq, which radically reduced the violence and set the stage for U.S. withdrawal beginning in 2010.

If Obama meets some or all of McChrystal’s request, America will stave off defeat in the short term. But the cost will be hundreds and perhaps thousands more U.S. dead, tens of billions more sunk, growing divisions in our country and more innocent Afghan victims. And the surge may simply push a U.S. withdrawal and Taliban takeover a few years off into the future.

This assumes that Afghanistan is unwinnable, that America does not have the perseverance or will to send the hundreds of thousands of U.S. troops for the decade needed to crush the Taliban and create a government and army able to stand on their own when we depart.

If, however, Obama comes to believe the cost of “victory” in blood, money and years is not worth it, or the American people, already against the war and adding more troops, will not sustain it, or the war is unwinnable, then we need to look defeat in the face.

For that is what McChrystal says we are risking, if Obama dithers or draws down troops.

Russia’s withdrawal of 1988-89 led to the collapse of the Soviet Empire. What would a U.S. withdrawal do to the American Empire?

A Taliban triumph would mean the Afghans who sided with us in this war would face the same retribution as our allies in Cambodia and Vietnam.

Western aid workers would have to flee the country.

Under Taliban control, Afghanistan would be a sanctuary for the Pakistani Taliban, which would be emboldened to settle scores with the Islamabad politicians who had sided with the United States.

Taliban allies in the Pakistan army and intelligence services would be seen as on the wise and winning side, while those who sided with America would be seen as losers. The odds would rise that Pakistan would face a revived insurgency and acts of terror against the regime. The odds on the survival of a pro-American regime in a country already marinated in anti-Americanism would fall.

Among Islamists worldwide, news that the Afghan Sunni Taliban had defeated and driven the United States out, as their fathers had the Soviet Empire, would be electrifying. Muslim governments aligned with America would be shaken and perhaps imperiled.

Al-Qaida, thwarted by U.S. security services and ravaged by U.S. Predator and Special Forces strikes, would be seen as having helped inflict a defeat on America unseen since Vietnam.

Osama bin Laden would be a candidate for Man of the Decade.

With his 9-11 attack, he had fired a shot heard ‘round the Islamic world, sucked America into two wars that bled, divided and helped to bankrupt her, and seen the last superpower off in Afghanistan.

Osama’s ultimate goal from the start—the removal of all U.S. troops from sacred Saudi soil and expulsion of all Crusaders from the Islamic world—would no longer be an impossible dream.

For America, loss of Afghanistan would poison U.S. politics as did the loss of China and of Vietnam. It would discredit nation-building for decades and ring down the curtain on Wilsonian interventionism for a generation. And it could bring about the defeat of Barack Obama as the liberal who lost the war al-Qaida began on 9-11.

Whether Obama cuts U.S. forces and advances the day of a Taliban victory, or doubles-down and sends the tens of thousands of U.S. troops Gen. McChrystal demands, Afghanistan has claimed another hubristic imperial power.