Britain has Brexited, choosing populism and over pragmatism, insularity over inclusion — and leaving the world transformed and deeply worried.

The rising tide against immigration has Trumped integration (pun intended, of course). It’s a script that Donald Trump, the presumptive Republican nominee, easily could have penned, were it not for the U.K.’s own version of nationalistic bombast and one of the standard bearers for Brexit — former London Mayor Boris Johnson. Johnson and other Brexit leaders hawked the idea of an anti-immigration, walled-off Britain, and Britons bought it.

The cascading fallout has already started. The pound has tumbled. World and U.S. markets are getting walloped as well. Prime Minister David Cameron, who backed Britain’s continued membership in the European Union, is already a casualty — he has told Queen Elizabeth he will resign.

But one of myriad takeaways from this globe-changing moment is that the face of the angry Everyman isn’t just blue collar, white male, and American. Resentment over feeling left out of the globalization party is just as real and pervasive in Britain — and even more worrisome — across Europe.

For America, Brexit should serve as a potent warning sign.

It will embolden Trump, who has already co-opted Brexit as validation of the populist themes buttressing his own campaign — wariness of outsiders, fortification of borders and an aversion to the notion of an integrated world. “I love to see people take their country back,” Trump said at a news conference at a golf course he owns in Scotland. “People want borders. They don’t necessarily want people pouring into their country that they don’t know who they are and where they come from.”

But it’s also the clearest indication yet of the power and toxicity of today’s tidal wave of populism. It’s not just grist for talk show monologues, not just a crazy quirk in one of most unusual presidential campaigns this country has ever seen. It can decimate currencies, upheave stock exchanges, wreck political careers and ultimately, change the world order.

With Brexit, the U.S.-U.K. relationship will suffer. President Barack Obama was quick to reassure, saying “the special relationship between the United States and the United Kingdom is enduring, and the United Kingdom’s membership in NATO remains a vital cornerstone of U.S. foreign, security and economic policy.”

But a Britain outside the EU is a weaker Britain, politically and economically. And one reason why Britain was such a valuable U.S. ally was that it has always been a strong, reliable voice in European and world affairs. Its geopolitical clout likely will diminish now. Economically, it faces a whole lot of turbulence and uncertainty. It will have to negotiate divorce terms with the EU, a betrayed body that isn’t likely to be amenable any time soon. And when it trades with the rest of the world, it will be on its own, without the political and economic heft that the EU brings to the table.

Britain will be forever changed by Thursday’s vote. It will have to reconnoiter, and conjure up a new course in a world where its voice likely will not be as strong. The EU will also have to take stock — other member countries have their own brands of nationalism thriving, and we may see more dominoes fall. But Brexit and the Trump phenomenon have exposed something else: A growing part of the world no longer sees strength in inclusiveness — instead it sees that as a threat. Brexit gave us a lot to mull, but maybe that’s what should have us most worried.

— Alex Rodriguez, a veteran foreign correspondent, is a member of the Chicago Tribune Editorial Board.