Amid a generational crisis in Canada’s relationship with the United States, the Liberal Party of Canada on Sunday chose an unelected technocrat with deep experience in financial markets to replace Justin Trudeau as party leader and the country’s prime minister, and to take on President Trump.

Mark Carney, 59, who steered the Bank of Canada through the 2008 global financial crisis and the Bank of England through Brexit, but who has never been elected to office, won a leadership race on Sunday against his friend and former finance minister, Chrystia Freeland.

He won a stunning 85.9 percent of the votes cast by Liberal Party members. More than 150,000 people voted, according to the party’s leaders.

“America is not Canada. And Canada never, ever, will be part of America in any way, shape or form,” Mr. Carney said in his acceptance speech on Sunday evening to an electric crowd of party faithful, directly addressing Mr. Trump’s constant threat that he wants to make Canada the 51st state. “We didn’t ask for this fight, but Canadians are always ready when someone else drops the gloves.’’

“So Americans should make no mistake,’’ Mr. Carney added. “In trade, as in hockey, Canada will win.”

He is expected to be sworn in as prime minister quickly, early this week, officially ending the Trudeau era. His first and most pressing challenge will be to manage the threat from Mr. Trump to Canada’s economy and sovereignty.