Republicans and Democrats are blaming one another for impending cuts to the defense budget brought about by sequestration. But with serial annual deficits of $1 trillion-plus and an aggregate debt nearing $17 trillion, the United States -- like an insolvent Rome and exhausted Great Britain of the past -- was bound to re-examine its expensive overseas commitments and strategic profile.

The president's nomination of Chuck Hagel for defense secretary was a sort of Zen-like way of having a Republican combat veteran orchestrate a reduced military. In fact, Barack Obama has nurtured a broad and diverse constituency for his neo-isolationist vision. Budget hawks concede that defense must suffer its fair share of cuts. Libertarians want back their republic and hate the big-government baggage that comes along with a big military's involvement overseas.

Leftists agree, adding that the U.S. has neither the moral authority nor the wherewithal to arrange events overseas. For liberals, a scaled-back military presence abroad means more entitlements at home. For each F-22 Raptor not built, about another 20,000 families could receive food stamps for a year.

The American public -- exhausted by Iraq and Afghanistan -- is receptive to all the above arguments. If our poorer grandparents thought 70% of the annual U.S. budget devoted to defense after the Korean War was about right, we, the more affluent, insist that even the present 20% is far too costly.

The result is that we lead from behind in Libya; France leads from the front in Mali. Syria and Iran shrug off Obama's periodic sermons to behave.

Our reset with Russia was abruptly reset by Russia. American policy in the Middle East could be summed up as "Whatever" -- as we become only mildly miffed that distasteful authoritarian allies are replaced by more distasteful Islamist enemies.

In his first major speech as secretary of state, John Kerry did not worry about radical Islam. Nor did he warn Americans of a rogue North Korea, a soon-to-be-nuclear Iran, or China -- bullying in the Pacific and cyber-hacking the U.S. -- but mostly of the need for collective efforts to address climate change. A shortage of solar panels and windmills, not impending cuts in U.S. ships and planes, is Kerry's idea of existential danger on the global horizon.

To the extent that there is a coherent American foreign policy, it is perhaps symbolized by drone assassinations: Every couple of days or so, just kill a terrorist suspect or two -- and as cheaply, as remotely and as quietly as possible.

What will the world look begin to look like as the global sheriff backs out of the world saloon with both guns holstered?

Japan and Germany, the world's third- and fourth-largest nations in terms of their gross domestic product, have never translated their formidable postwar economic strength into their past, prewar levels of military power. Yet both in theory could quickly do so -- and make nukes in the same way they make fine cars -- once they sense that there is no longer an unshakable U.S. commitment and ability to shelter them from regional threats. In fact, an array of allies -- South Korea, Taiwan, the Philippines -- would all be frontline garrison states should the U.S. military vacate their bad neighborhoods.

The world is full of hot spots apart from the Israeli-Palestinian dispute. Shiite majorities in many of the Sunni-ruled and oil-rich Persian Gulf kingdoms believe that a terrorist-sponsoring Iran is more a liberator than rogue nation, and that Gulf oil has not been fully utilized as a strategic weapon.

The Aegean, Cyprus, the former Soviet Republics, the Falkland Islands, Central America and the Baltic are all deceptively quiet. Potentially aggressive actors in the region don't quite know how the U.S. military might react -- only that it easily could, and has in the past.

We lament the terrible American losses in blood and treasure in tribal Afghanistan and Iraq. But privately, radical Islamists acknowledge that the U.S. military killed thousands of jihadists in both countries -- and hope never to see U.S. troops on the battlefield again.

Of course, a country that can neither budget the necessary money nor maintain the will to oversee the international peace has no business continuing to try.

But in our relief from the vast costs and burdens of maintaining the postwar global order, we might at least acknowledge the truth, past and present: Just as the world was a far better place after 1945 because of an engaged United States, so it will probably become a much worse place due to an increasingly absent America.