U.S. foreign policy isn't dead. Yet.

The foreign-policy community is furiously debating what grand strategy America should pursue in an age of accelerating international rivalry. But what if America, whipsawed by populism, polarization and disillusion, is becoming incapable of pursuing any grand strategy whatsoever?

This dreary prognosis has become more common as academics and policy analysts grapple with the causes and consequences of Donald Trump's presidency. And although there is good reason to worry, it is too soon to pronounce the passing of American internationalism just yet.

The most recent exposition of the "It's all over" thesis comes from Daniel Drezner of Tufts University. In a provocative essay and an accompanying blog post, Drezner argues that the problem with U.S. foreign policy is not simply that American power is declining. It is that the political foundations of American statecraft have crumbled.

"The Blob," to use a term popularized by top Obama adviser Ben Rhodes, has been discredited by unpopular wars in Iraq and Afghanistan. The longstanding bipartisan consensus on American global engagement has been replaced by intensifying polarization that causes wild gyrations whenever the White House changes hands. The American people have simply become less interested in foreign affairs since the end of the Cold War. And as President Trump has disrupted American diplomacy, the normal checks and balances — Congress and the courts — have more often deferred to than restrained the president.

The result is that U.S. foreign policy seems ever less credible and constant at a time when the world badly needs a steadying hand. Inertia and tradition will keep the American world order together for a while, but as countries lose confidence in America, the system will ultimately break down.

I have a fair amount of sympathy for this argument. In our recent book, "The Lessons of Tragedy," Charles Edel and I argue that America's success in creating such a benign, prosperous world has, ironically, made it possible for Americans to forget why they should be so deeply involved in the world in the first place. It is indisputable that the end of the Cold War made it harder for Americans to intuitively grasp the purpose of U.S. alliances and other overseas commitments. In all but one presidential election since 1992, in fact, Americans have chosen the presidential candidate who promised to be more restrained in world affairs than the candidate who promised to be more active. According to a 2016 poll by the Pew Research Center, a record number of Americans — 57 percent — believed that the U.S. should basically mind its business and let other countries handle their own. As for the Blob and its misjudgments, it is no coincidence that America's two most recent presidents — a Democrat and a Republican alike — have both found it profitable to use the foreign policy elite as a political whipping boy.

Finally, while the degree of the present political polarization is sometimes exaggerated, the problem is getting worse. After all, Trump unsigned not one but three major international accords — the Paris climate change agreements, the Iran nuclear deal and the Trans-Pacific Partnership — that the Obama administration spent years creating. There are unmistakable signs of decay in the internationalist consensus, and if that decay advances it will have profound implications for America's ability to preserve the world it has built.

Second, the political foundations of U.S. foreign policy have been tested before, and they have survived pressures that seemed far worse than the ones at work today. In the mid-1970s, the Vietnam War had discredited an earlier foreign policy elite — the "best and the brightest" — even more thoroughly than the Iraq War discredited the Blob. Polarization was intense and often violent; pursuing a centrist foreign policy seemed impossible. American will and commitment were in serious doubt: In the wake of Vietnam, only 36 percent of those surveyed believed "it was important for the United States to make and keep commitments to other nations." Within a few years, however, the traumas inflicted by Vietnam were easing. The Cold War consensus was reasserting itself, as aggressive Soviet behavior reminded Americans why the superpower rivalry needed waging.

This relates to a third reason for optimism: One can now see, however faintly, the outlines of a new consensus. Since the Cold War, policymakers have struggled to persuade Americans that there is a threat against which the U.S.-led international system needed to be defended. But that threat is rapidly presenting itself today, in the form of aggressive behavior by hostile authoritarian powers.

Russia's election-meddling in the U.S. has produced a bipartisan desire to better compete with the Kremlin, as demonstrated by broad support for enhancing NATO's defenses and keeping Moscow under sanctions. Trump and some of his die-hard followers may be pro-Putin, in other words, but hardly anyone else is.

The emergence of an increasingly global challenge from China has also stimulated widespread alarm. A bipartisan group of senators and representatives has been pushing to sanction Chinese officials involved in the appalling repression of the Uighur population of Xinjiang. And as two experts from the American Enterprise Institute have noted, China's military buildup, predatory economic policies and dismal human rights record are eliciting calls on both sides of the aisle for a sharper response. Indeed, the China threat is pushing conservatives and liberals alike to take positions that would have been hard to imagine only a few years ago. When progressives such as Elizabeth Warren are starting to sound like Harry Truman in identifying a new global authoritarian threat to democracy, when conservatives such as Marco Rubio are calling for a national industrial strategy to ensure U.S. economic competitiveness, one gets the sense that a new foreign-policy consensus may be forming.

In the past, what has tended to rally Americans to support an engaged foreign policy has been the prospect that rival great powers, motivated by hostile, anti-democratic ideologies, might otherwise gain the global ascendancy. Perhaps this prospect will once again reinvigorate American internationalism before it is too late.