The dispute comes amid worsening trade relations between the allies.
The new levies were set to go into effect early Wednesday.
Ambassador Pete Hoekstra is accused of normalizing diplomatic attacks on Canada.
Canada on Friday celebrated the completion of a new bridge to the U.S. over the Detroit River, cutting a ceremonial ribbon on a multibillion-dollar, multiyear project that will serve as a critical path for trade, jobs and tourism between the countries.
The tariffs will take effect 30 days from now.
The leader of Canada's Ontario province on Saturday lashed out at President Donald Trump over his threat to add "the cost of pollution" from that country's wildfires to US tariffs.