Henry Nicholls / Reuters

In the 1980s, a group of anti-Communist student activists in Poland popularized the slogan “Smile! Tomorrow will be worse.” Those words apply well to Donald Trump’s diplomacy.

On Thursday, Trump brought chaos to a NATO summit. Friday will be his day to apply his special touch to the U.S.–U.K. relationship.

This is a moment when America’s closest security partner badly needs American help. In 2016, 51.9 percent of the British public who voted in the Brexit referendum opted to quit the European Union. The leaders of the “Leave” campaign assured voters that the U.K. would easily and speedily negotiate a favorable new relationship with the truncated EU. They promised, too, that a post-EU Britain would negotiate new trade pacts with the United States and Canada. In the words of the Vote Leave campaign’s manifesto:

We will negotiate a new UK-EU deal based on free trade and friendly cooperation. We will carry on trading with Europe but we will also be able to negotiate trade agreements with other countries. This will help our economy grow and create more jobs …

The UK is the EU’s single largest export market in goods, taking a larger share of EU exports than even the United States. It is in everyone’s interests, particularly Germany’s, to negotiate a friendly UK-EU free trade deal ...

If we Vote Leave and take back control of our trade policy, we can speak for ourselves and sign new deals with countries all over the world, creating new jobs and new investment opportunities.

The Brexit champion Boris Johnson expressed the promise more vividly. Acknowledging that in the interim Brexit might cause “some plaster to come off the ceiling,” he foresaw a glorious new era of U.K.-negotiated trade deals: “Think what we can do when we have free-trade deals with America, where they still have a ban on British haggis. Think of our potential whiskey sales to India if only we could negotiate a cut in their duty of 150 percent on Scotch.”

Twenty-five months later, there has been scant to zero progress on those former high hopes. As things stand, the U.K. is headed toward the hardest of hard exits at the deadline of March 29, 2019.

The British have made this bed, but it is not in America’s interest to abandon them to lie in it.

A more normal U.S. president would have already accepted responsibility for the EU–U.K. problem as a major foreign-policy challenge—and would have intervened to help America’s friends on both sides of the impasse. But Trump is not normal.

Every U.S. president from Dwight Eisenhower to Barack Obama favored an integrated European economy with Britain on the inside. President Trump favored Brexit in 2016. Having gotten his wish, he has turned his back on his Brexiteer friends. The Leave campaign imagined that Brexit Britain would seamlessly transition from the EU to a new Anglosphere trading future. Instead, negotiations with the United States have barely begun—no surprise in this chaotic administration. (The chief trade negotiator for agriculture did not even take office until March 1.)

As Thomas Wright noted in Politico, rather than negotiate a U.S.–U.K. free trade pact, Trump has hit Britain with bogus national-security tariffs on steel and aluminum. His administration offered the U.K. an open-skies agreement on passenger aviation inferior to what the U.K. had enjoyed as a member of the EU, and is dropping broad hints that Britain may have to dismantle important elements of its cherished National Health Service as part of any future U.S.–U.K. trade deal.

Rather than soothe difficulties between the U.K. and EU, the Trump administration has inflamed them. In October 2017, the Trump administration joined with Canada, New Zealand, and other food exporters to disrupt a U.K.–EU agreement at the World Trade Organization over agricultural trade.

Mostly, though, the Trump administration has adopted a policy of malign neglect to the U.K.–EU portfolio. Trump cannot coax or nudge the two sides closer together. Trump’s avidity to topple Merkel’s government in Germany obviously gets in the way of enticing concessions from that government for the benefit of the U.K. Trump tweeted in June that “the people of Germany are turning against their leadership.” (Merkel’s approval rating is 51 percent, much higher than Trump’s.) His ambassador-provocateur expressed a wish for a more right-wing German government in a Breitbart interview in his first week on the job.

At the EU’s center, the Trump administration is utterly AWOL. Trump did not get around to nominating a U.S. ambassador to the EU until March, and the nominee did not arrive in Brussels until July 9. The chosen ambassador—a longtime Republican fundraiser—owns a small chain of hotels, but otherwise has little background or expertise in trade issues.

In the year before the EU vote, the U.K. was the best-performing economy in the G7; since the midsummer of 2016, it has vied with Japan for last place. The U.K. and the United States are each other’s largest investor. Despite severe cuts after the 2008 financial crisis, the U.K. has stabilized defense spending and remains above NATO’s 2-percent-of-GDP target.

A poorer, more vulnerable, more inward-looking Britain will dwindle into a less-reliable partner for the United States. A close U.S. friend is in big trouble, and it should be in America’s high interest to help. But helping friends is not in Donald Trump’s nature or competence—and once this thin-skinned and unstable president catches a glimpse of that satirical big orange baby blimp over the skies of London, he’s likely to be confirmed in his apparent bedrock conviction that Vladimir Putin is the only overseas friend he’s got.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.