tl;dr: US-Canada trade talks collapsed Friday night after PM Mark Carney rejected "last-minute changes" to US terms, prompting new 50% US tariffs on about 5% of Canadian exports including wine, dairy, cement, and clothing under the Tariff Act of 1930. Canada will retaliate "dollar for dollar," and analysts estimate the tariffs could cut Canadian GDP by 0.3%-0.6%. The breakdown reverses earlier optimism about a deal that would have reduced tariffs on steel, aluminum, and autos in exchange for Canada restoring US alcohol sales.