tl;dr: US-Canada trade talks collapsed Friday night after PM Mark Carney rejected last-minute US changes he called "unfair and uneconomic," triggering new 50% US tariffs on roughly 5% of Canadian exports including wine, dairy, cement, and clothing. Carney pledged dollar-for-dollar retaliation, ending negotiations that had been close to reducing tariffs on steel, aluminum, and autos. Analysts estimate the new tariffs could cut Canadian GDP by 0.3% to 0.6%, with Ontario, Quebec, and British Columbia most exposed.