Wet flurries blanketed a sombre Oshawa as hundreds of workers quietly shuffled out of the General Motors assembly plant as they finished work for the day. Many were still processing the previous day’s devastating news: by next year, the plant – the city’s main employer – would be no more.

GM announced on Monday that it was closing three North American car plants – in Oshawa, Ontario, Lordstown, Ohio, and the Hamtramck plant in Detroit – and two additional facilities in Warren, Michigan, and Baltimore, Maryland. About 14,700 jobs are on the line.

A day later, the consequences for this Canadian city 31 miles north-east of Toronto were still sinking in.

“This place has always thrived because of the plant. GM is Oshawa. That’s who we are,” said Andrea Bourke, a lifelong resident of the city.

Automotive assembly is inextricable from Oshawa’s history: companies began building cars in the city more than 100 years ago. At one point, the Oshawa facility was the largest car manufacturer in the world, pumping out vehicles for Canada, the US, South America and the Middle East.

The sprawling 10m sq ft of the assembly plant is difficult to miss in a city of 160,000. “This place is iconic,” said Jerry Wheeler, an employee at the plant and union representative. “It’s like a symbol of this city.”

But, according to GM, times have changed. Chief executive Mary Barra said the company was reacting to slow sales of sedans and rising costs from Donald Trump’s steel and aluminium tariffs. Fear of an economic slowdown and falling car sales have probably steered her decision too.

Following the announcement, employees were left wondering how a plant that has received numerous awards – and is considered by GM to be one of the most efficient within the company’s large portfolio – could be shutting down.

“I felt bad when I heard the news,” said Danny Toms, a GM employee of 35 years. “But I feel worse for the younger generation. I’ll get my pension. They’ve got no jobs on the horizon.”

Within Canada, the plant was held in high esteem: last year, it placed in fourth the best places to work in Canada survey, and ranked first for wages and benefits.

“People are very disappointed. They’re worried. How are they going to find their next job? A lot of workers are in their 50s. It’s not easy,” said Joe Kanniah, owner of a sports bar directly across from the plant where employees relax after a shift or grab a quick lunch.

He worried the job losses would affect his business, a sentiment he said is shared throughout the community. The reach of the company far exceeds the physical plant and the large portion of the city it employs.

Oshawa’s junior hockey team, the Generals, gets its name from the first sponsor: General Motors. It’s home to the Canadian Automotive Museum. The home of GM Canada’s founder, Samuel McLaughlin, is now a national historic site.

Across the border, 300 miles south in Lordstown, Ohio factory workers were feeling much the same. “It’s disgusting, my stomach hurts,” Cheryl Jonesco said after learning she would lose her job. “It’s just disgusting”.

“I think this will light a fire under us,” said Jonesco, 40, who has worked at the plant for 10 years on the assembly line and installed the rear-view cameras on the Chevy Cruze – one of the models GM will no longer make in North America. “You just can’t sit back and do nothing and throw your hands up, it’s not an option at all.”

It’s not just workers who are angry. The political backlash to the move is just getting started. Trump and Canadian prime minister Justin Trudeau have expressed their disappointment with GM. Both countries gave billions to GM and other car companies after they nearly went bust in the last recession.

On Tuesday the US president threatened to cut all of GM’s subsidies. “General Motors made a big China bet years ago when they built plants there (and in Mexico) – don’t think that bet is going to pay off. I am here to protect America’s Workers!” he tweeted.

To many workers, the decision to close the plant felt like a betrayal after years of concessions to keep the company profitable during the worst days of the recession.

GM’s closures are a particularly bitter blow in Ohio’s Mahoning Valley, where the plant was one of the last large manufacturers in a region that once employed thousands in steel plants and factories.

“That plant is the economic lifeline of the whole valley,” Lordstown mayor Arno Hill told Associated Press. “When we lost steel, that plant carried us through.”

While the news has hit hard in Oshawa, it is not without precedent; the residents of Oshawa have suffered the jarring blows of industry slow downs over the years. Jobs looked precarious as recently as 2009, when GM Canada was on the verge of bankruptcy, saved only by a last-minute $10bn loan from the Canadian government.

Jerry Dias, president of Unifor, the Canadian car workers union, is angry. In a fiery speech to more than a thousand employees, the union leader pledged to challenge the decision, lobbying as high was possible. “They are not closing our damn plant without one hell of a fight,” he told a frustrated crowd.

On Tuesday afternoon, he met Trudeau in Ottawa – an indication of the critical influence of the plant on both the city and the broader Canadian economy. The abrupt closure has become fodder for politicians of all stripes, each blaming the other’s present or past policies for leading to GM’s decisions.

But for many employees, politics was a secondary concern. First and foremost: the closure felt like the ultimate betrayal of their loyalty.

“I’ve always said, if you come to my house, you’d better be driving a GM car,” said Wheeler, a 34-year veteran of the company. “Not any more. How can I support a company that stabs its employees in the back right before Christmas?”