Perhaps unexpectedly, Trump’s abrupt withdrawal from the Iran nuclear deal exposed America’s weak hand. For we left — but then what? In different circumstances — after negotiations, after obtaining proof that Iran was in violation of the deal — it might have been possible to recreate the international coalition that imposed sanctions so successfully in the first place. In different circumstances, it might also have been possible to change the deal: That’s what the French president and German chancellor were offering during their recent visits to Washington, though their efforts were rebuffed. In different circumstances, it might even have been possible to threaten Iran militarily — not a position I advocate, but I can imagine how it could be done.

Instead, we are now in the worst of all possible worlds. We have broken the agreement with Iran, but we are unable to impose a new sanctions regime in its place. Instead of making a diplomatic investment, we are shouting and barking orders. Just after Trump’s announcement, the American ambassador to Germany issued a threat on Twitter: “German companies doing business in Iran should wind down operations immediately.” As a result, European leaders are not talking about Iran. They are talking about how they can protect their companies from American sanctions, and how they might retaliate.