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.