"Based on their egregious behavior, ALL TRADE NEGOTIATIONS WITH CANADA ARE HEREBY TERMINATED," Trump wrote on Truth Social on Thursday.
Ontario Premier Doug Ford earlier this week said the ad with anti-tariff messaging had caught Trump's attention.
The ad showed Reagan, a Republican, criticising tariffs on foreign goods while saying they caused job losses and trade wars.
"I heard that the president heard our ad. I'm sure he wasn't too happy," Ford said.
The Ronald Reagan Presidential Foundation issued a statement saying the ad by the government of Ontario was "using selective audio and video" of Reagan and that the foundation was reviewing its legal options.
"The ad misrepresents the Presidential Radio Address (by Reagan in 1987), and the Government of Ontario did not seek nor receive permission to use and edit the remarks," the foundation said in its statement.
The Canadian government had no immediate comment.
Trump has used tariffs as leverage on many countries around the world.
His trade war has increased US tariffs to their highest levels since the 1930s and he has regularly threatened more duties, sparking concerns among businesses and economists.
Canadian Prime Minister Mark Carney told reporters on Thursday that Canada would not allow unfair US access to its markets if talks on various trade deals with Washington fail.
Trump imposed tariffs on Canadian steel, aluminium and autos earlier in 2025, prompting Ottawa to respond in kind. The two sides have been in talks for weeks on a potential deal for the steel and aluminium sectors.
In 2026, the United States, Canada and Mexico are due to review their 2020 continental free-trade agreement.
