Alcohol has landed on the front lines of a global trade war, throwing French wines, Irish whiskeys, Kentucky bourbon, Japanese beer and Mexican tequila into the crossfire between the U.S. and its biggest trading partners.

In the Canadian province of Ontario, liquor stores have cleared their shelves of California wine and Tennessee whiskey, replacing them with local varieties and signs declaring: “For the good of Canada.” A restaurant wine director in Washington state is dreading the arrival of shipping containers full of European wine so expensive it’s unsellable. The Kentucky governor is pleading for the survival of his bourbon industry. And makers of American sparkling wines are poised to make a windfall.

President Trump on Thursday opened a new front, threatening a 200% tariff on U.S. imports of all alcoholic beverages from the European Union. Trump’s salvo was a response to the EU’s decision to move forward on a 50% levy on American whiskey.

Thursday’s escalation caused panic on both sides of the Atlantic.

The EU exported wine worth more than $5 billion to the U.S. last year, according to EU data agency Eurostat. Almost half of that came from France and about 40% came from Italy.

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A 200% tariff would push many bottles on store shelves above the $20 range that many American wine drinkers find acceptable, said Lamberto Frescobaldi, patriarch of the Italian winemaking dynasty that spans 30 generations. Above that price range, he said, “most people probably are not going to buy.”

Remi Cohen, chief executive of the small California producer Domaine Carneros in California’s Napa and Sonoma counties, was sitting in her hot tub Thursday morning when she saw the tariff headlines on her phone and felt her heart rate jump. A maker of domestic sparkling wines and pinot noir, she seemed an obvious candidate to rejoice at the news. But the winery, owned by France’s Taittinger family and the American Kopf wine-distributor family, was already being buffeted by Trump’s tariff wars.

In anticipation of U.S. tariffs on steel, the winery late last year had ordered steel it needed for trellises to replant a portion of its vineyards. More recently, the winery has been discussing what to do about tariffs on Canadian and Mexican imports, which could affect the price of glass bottles.

Now a tariff on European alcohol could hurt the ecosystem of retailers, distributors and restaurants Domaine Carneros depends on, Cohen said. “If they’re adversely affected, pain will be felt throughout the entire industry,” she said.

Photos: Getty Images, iStock Alana Pipe/WSJ

To be sure, a 200% tariff on European alcohol might never materialize. It could be delayed, scaled back or imposed for just a few days. Trump in February was poised to implement 25% tariffs on all imports from Canada and Mexico—including Canadian whisky and Mexican tequila—and at the 11th hour delayed them for a month. The tariffs then briefly went into effect this month before largely being put on pause.

That didn’t stop Ontario Premier Doug Ford from firing back with a reciprocal assault on American alcohol.

The Liquor Control Board of Ontario pulled American booze from store shelves and told bars, restaurants, supermarkets and convenience stores they could no longer place orders for U.S. products.

“The governor of Kentucky said ‘Don’t touch our bourbon.’ I said, ‘Governor, that’s the first thing we’re going after,’” Ford said at a recent news conference. “For Kentucky bourbon manufacturers, they’re done, they’re gone.”

Others are taking action, too. Asahi Group , one of Japan’s largest drink makers, this week said it was investing tens of millions of dollars to start and boost production of its top-selling Asahi Super Dry beer at a plant it acquired last year in Wisconsin. Asahi has been importing the beer brand to the U.S. from Italy, so it could be affected by potential U.S. tariffs on European products.

“We can’t ignore that,” Asahi Chief Executive Atsushi Katsuki said.

‘Drank up at the right time!’

Erik Liedholm, the wine director for three restaurants in Washington state, said he learned about Trump’s latest threat Thursday when his phone “blew up” with texts and emails from friends in the wine business who sell to Canada and Europe.

“They were just saying, ‘What do I do? What do I do?’ I looked at the trail of texts and it was just extraordinary,” Liedholm said. “I was speechless.”

One of the messages was an email from his wine importer, telling him that prices would be going up.

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“Our margins are getting thinner and thinner,” Liedholm said. With shipments currently en route, “it’s almost like the boats are arriving with the plague.”

If a 200% tariff did go into effect, here’s how it would work: A bottle of Champagne that sells for $50 at retail typically costs an importer about $20. With a 200% tariff, the importer’s cost would triple to $60. If the importer and retailer preserved their combined profit margin of $30, that $50 of bubbly would have a new sticker price of $90.

But importers say the more likely scenario is that they would simply stop importing altogether. Because those bottles just wouldn’t sell.

Tariffs on European alcohol could boost the fortunes of American wineries whose bottles compete with European imports. Makers of domestic sparkling wines could benefit if Champagne and prosecco prices soar, for example.

But levies are unlikely to transform the domestic wine industry, said some winemakers. That’s because European wines make up a minority of wines sold in the U.S.

Oren Lewin is chief executive of IBG Wines, whose portfolio includes Oregon Pinot Noirs under the Duck Pond Cellars, Rascal and Firesteed labels. They could serve as alternatives to European burgundies, Lewin said, but he is stopping short of adjusting the company’s business plans in preparation for potential tariffs.

“We don’t worry about what we can’t control,” he said.

Cedric Nicaise, a co-owner and sommelier at the Noortwyck in Manhattan, said he isn’t so sure that American consumers would change their drinking habits. He was drinking coffee Thursday morning when he received a text from a regular customer, with whom he had shared a glass of Marquis d’Angerville Volnay the night before. The message said: “Drank up at the right time!”

Nicaise buys between 30 and 35 cases of wine a month for his restaurant. The majority is French, Italian or Spanish.

“If you drink Burgundy, you might drink a Pinot Noir—but you might drink a cocktail,” Nicaise said. “You don’t just switch to American wine. You drink French wine for a reason.”

Write to Laura Cooper at laura.cooper@wsj.com , Juliet Chung at Juliet.Chung@wsj.com and Stacy Meichtry at Stacy.Meichtry@wsj.com