Catalans speak their own language. They are richer than their fellow citizens in the rest of Spain, and thus contribute more to the national budget than they receive back. They carry unhappy memories of domination by centralizing governments in Madrid. The Franco dictatorship of 1939-1975 harshly suppressed their culture, identity, and political and civil liberties. It’s a pure accident of history that Catalonia ended up inside the Kingdom of Spain at all. Portugal successfully broke away in the 1640s. Had the Thirty Years War, the War of Spanish Succession, or the Napoleonic wars taken a slightly different turn, Catalonia might well have followed.

All this may seem long ago and far away to the American reader. But it’s all suddenly very top of mind for modern Europe. The Catalan regional government has invited its population to vote Sunday in a referendum on independence. The referendum has been declared illegal by the Spanish Constitutional Court, because it violates the terms of the 1978 constitution that proclaimed Spanish unity “indissoluble.” The central government has reacted roughly to the referendum project, raiding local government offices, impounding ballots, and arresting local officials. “Stop this escalation of radicalism and disobedience,” the Spanish prime minister commanded in a televised statement on September 17th.  Unsurprisingly, those words failed to calm the situation. The streets of Barcelona have filled with protesters. Only about 40 percent of Catalans favored independence as of midsummer, but feelings are running hotter now.

Prime Minister Mariano Rajoy visited Washington, D.C. on September 26th. At a joint press conference, President Trump deplored the secession vote.

I think the people of Catalonia have been talking about this for a long time.  But I bet you if you had accurate numbers and accurate polling, you'd find that they love their country, they love Spain, and they wouldn't leave.  So I'm just for united Spain.  

I speak as the President of the United States, as somebody that has great respect for your President, and also has really great respect for your country.  I really think the people of Catalonia would stay with Spain.  I think it would be foolish not to.  Because you're talking about staying with a truly great, beautiful, and very historic country.

(The formal title of the prime minister of Spain is “president of the government,” hence Trump’s reference to him as “your president.”)

Trump’s words are unlikely to cut into separatist sympathy in Catalonia. A Pew survey found that 92 percent of Spaniards have no confidence in him, his worst rating in any European country surveyed. Yet Trump was—for once—speaking on behalf of the United States in a way that America’s friends in Spain need to hear.

Perhaps a better way to understand the issues at stake is to take note of which international actors support the independence referendum: Julian Assange and Russian propaganda outfits, to the extent that those are different things. The main effort of Sputnik’s Spanish-language Russian propaganda has been to shade its reporting to suggest easy entry into the European Union for an independent Catalonia.

Catalan nationalism has historically had a left-of-center flavor, unlike other Russian-favored secessionist movements in Europe. But the Russian interest seems, as usual, less about ideology and more about creating chaos, not only for Spain, but within the European Union. Carving up an economy of more than a trillion euros (and apportioning a public debt very nearly equally as large) will generate endless problems for Catalans and whatever remains of Spain.

The American interest has historically been just the opposite: continuity, stability, and the preservation of established institutions. Pre-presidential Trump departed from this norm, with his sympathy for British exit from the European Union. Presidential Trump has at least been furnished with better talking points.

But not for the first time, Americans and the world face the cost of a president who commands so little respect on the world stage, atop an administration already nearly as dysfunctional as Putin could wish. There is no U.S. ambassador to Spain, among other indicators of the breakdown of foreign policy function.

Very possibly, America and the West will get lucky. The Madrid authorities will behave less provocatively; the Catalans will vote “no”—or better yet, not show up to vote at all. (Only 40 percent of Catalans showed up for the last independence vote, in 2014, making irrelevant the 80 percent “yes” outcome.) But how long can luck hold? The harms from a U.S. presidency concerned only for the president’s own personal interests are accumulating and accelerating, month by month, week by week.