"Canada wants the benefits of being a State, without being one!!!" Trump wrote on Truth Social.
Trump also accused Canada of imposing massive tariffs on American farmers for many years.
The remarks were Trump's first public comments since the latest round of trade negotiations failed, paving the way for new 50% US tariffs on a range of Canadian goods.
Canadian Prime Minister Mark Carney responded by announcing that Ottawa would match Washington's new tariffs dollar-for-dollar to protect Canadian workers, farmers, families and businesses.
"They will be concentrated in sectors such as steel, dairy, appliances, agricultural equipment, pulp and paper, and electronics," Carney said.
"This will also include products currently subject to the unjustified Section 232 and 338 tariffs. This is a focused response to protect and defend our industries and allow them to compete with US products in the Canadian market," he added.
Carney said details of the new measures would be released in the coming days and that the tariffs would come into force on the Tuesday after Labour Day.
"We cannot accept what they have offered, and we will not give what they have asked," Carney said.
The negotiations followed Trump's last-minute decision to delay the planned tariffs by three days, giving the two countries additional time to reach an agreement. The original tariffs were scheduled to take effect on August 19.
Trump's latest "Canada state" remark echoes his repeated references to making Canada the "51st state" of the United States since returning to office.