President Trump's ban on Canadian alcoholic beverages worth $800 million annually took effect Tuesday, marking an unprecedented escalation in US-Canada trade tensions. The ban includes exemptions for whisky and liqueurs in containers larger than four liters, though experts say most American consumers are unlikely to immediately notice due to stockpiling and workarounds. Trump expects Canada to negotiate a deal soon, but the measure reflects deepening tit-for-tat tariffs and import restrictions between the two countries.