U.S. foreign policy for decades proceeded in the shadow of the failure in Vietnam. Some 58,000 Americans were killed in that war. Stateside protests were fierce enough to persuade President Lyndon Johnson to sit out the '68 election. Seven years later, after about 2 million civilian Vietnamese deaths, the U.S. finally gave up without having prevented a Communist takeover of the country.

"Vietnam syndrome" restricted our foreign conflicts, for a time, to such swift and relatively petty adventures as 1983's post-coup invasion of Grenada (which, though it involved fewer than 8,000 U.S. troops, did kill 19 U.S. soldiers, wound 116 more, and prompt a massive majority of the U.N. General Assembly to dub the American action a "flagrant violation of international law") and the 1989 overthrow of troublesome Panamanian leader Manuel Noriega.

But in 1991, the U.S. resumed big-time war waging in order to reverse Iraq's conquest of Kuwait. Along with 38 allied countries, America commanded more than 600,000 troops in a three-month ground war. The Bill Clinton era meanwhile saw U.S. overseas interventions begin to be characterized as "humanitarian." We dipped in and out, sending troops or war planes to Somalia, Haiti, Bosnia, and Kosovo and helping to displace over a million people combined.

After September 11, 2001, the U.S. military fully re-entered the world stage. The last 17 years have seen a variety of wars, quasiwars, and ongoing interventions with a mix of shifting rationales, from revenge for the attacks to spreading peaceful democracy in the Middle East to targeting specific bad actors to simply helping our Saudi allies as they work to reduce Yemen to a charnel house. None of these more recent efforts have worked out well on a geopolitical level. Meant to end Islamic terrorism worldwide, our post-9/11 warmaking multiplied it. A 2007 study by NYU researchers found that the average yearly number and fatality rate of terror attacks rose by 607 percent and 237 percent respectively after we entered Iraq in 2003. If you exclude violence in that country, the increases were still 265 and 58 percent; most jihadis in subsequent years were radicalized by the invasion itself.

Meant to crush Al Qaeda, our interventions have expanded its breadth and numbers; meant to create stable democracies in the Middle East, they've helped reduce Iraq, Libya, Syria, and Yemen to the same sort of chaos that bred the terror in Afghanistan that began this whole bloody, pointless process.

The domestic politics of foreign policy have changed tremendously, however, thanks to a 21st century innovation that permanently altered the political calculus of foreign intervention for the United States: the drone.

The federal government has been reluctant to reveal unvarnished facts about the rules of engagement or the results of our 16 years of droning all across the Middle East, so we have no choice but to rely on often-conflicting estimates from civilian research groups employing different sources and methods. A moderate estimate is that we have likely conducted more than 1,200 such strikes against Libya, Pakistan, Somalia, and Yemen and likely killed over 2,000 militants (in addition to many hundreds of innocent civilians, the latter being "collateral damage" in Pentagon parlance). Back home, the most important aspect of all this death and destruction is that it doesn't involve a single American boy coming home in a body bag—thus rendering our interventions all but invisible to American voters and reducing the electoral cost to pretty much nothing.

We have not stopped putting boots on the ground; we just deploy fewer of them with less fanfare. Thousands of U.S. troops are embedded in the madness of Syria and in Afghanistan, despite candidate Donald Trump's suggestions that he would pull our people out.

And though we may be warring differently, our rationale for visiting calamity on the rest of the world feels quite familiar. We haven't given up opposing our former Soviet foe, continuing to train troops, sell arms, and fork over hundreds of millions of dollars in military aid to Russia's Ukrainian rivals. Despite being manifestly terrible at it, we still pretend our absurdly large advantage in arms can make us a successful hegemon, shaping the world by force.

President Trump is more openly hostile to Iran than was his predecessor. He abrogated President Barack Obama's nuclear deal, and there is overall little sign his administration is prepared to seriously rethink our ineffective Middle Eastern postures. The pettiness of his trade war with China also does not bode well for relations with our most realistic future rival in the hegemon category.

These various post-9/11 foreign policy failures have cost our debt-riddled nation at least $1.5 trillion in direct costs, according to a recent Defense Department report, and more than $5 trillion in ancillary costs—such as interest and future veterans expenses—according to a 2017 analysis by the Watson Center at Brown University. In constant 2018 dollars, the Defense Department will spend this year in excess of 50 percent more than it did in 1968.

But the more hideous cost—especially poignant for those who remember the cries of "Hey, hey, LBJ, how many kids did you kill today?"—is in lives. That same Watson Center study estimates that there have been 370,000 deaths from direct war violence since 2001; 200,000 civilian deaths; and over 10 million people displaced by the harm to property and municipal functionality. Alas, this human and social misery is obscured by consistent, deliberate use of bloodless rhetoric. American foreign policy professionals and pundits somehow manage to look at our costly failings and the world's suffering—all that money, all that death—and think the answer is that the U.S. military should have done more, and smarter, and harder.

As The Washington Post paraphrased a phone call from then–Secretary of State Hillary Clinton to a Pakistani official in 2012, "The United States reserved the right to attack anyone who it determined posed a direct threat to U.S. national security anywhere in the world." Over many administrations, that remains the core of U.S. foreign policy.

If only the lessons of Vietnam, or even of Iraq, would actually stick. We can't expect the aftereffects of this century's foreign policy sins to be short-lived. Laos still suffers dozens of deaths a year because of 80 million unexploded bombs left behind by the Vietnam War. The casualties of our drone wars may be their own variety of unexploded ordnance, as generations grow up in the literal and figurative shadows of insufficiently discriminating robot death machines in the sky, courtesy of the United States.