Canada has a much smaller population than the U.S. There are more dairy farms in Wisconsin than the whole country of Canada. American farmers overproduce milk and end up dumping unused supplies. If Canada lowers its tariff, cheaper American milk will flood the market and kill Canada's dairy industry.
All countries have some high tariffs to protect their interests. America has a 350% tariff on tobacco to protect their farmers. What Trump doesn't mention is that Canada's average tariff is 0.85 – one of the lowest.
