Trump this spring imposed a 25% tariff on cars and car parts, including those from Canada. But certain cars and parts qualify for preferential treatment under the USMCA, meaning the 25% tariff applies only to the non-U.S. content of the automobile or part.

The letter reiterated Trump’s complaints about dairy quotas, fentanyl and the U.S. trade deficit, which is mostly fueled by American refineries’ thirst for Canadian oil. His social media post caused the Canadian dollar to immediately tumble, indicating the market wasn’t expecting this escalation.