"Whether or not they ever be put into place, the damage is done," said Greig Mordue, a former auto industry executive and associate professor at the W. Booth School of Engineering Practice and Technology at McMaster University.

He says Trump's threats have already changed the landscape. Whether he goes ahead with the tariffs or not, or whether he carves out specific exemptions, the threat alone will drive investment out of Canada and into the U.S.

"For at least the next four years, there will be no serious investment in the Canadian automotive industry," said Mordue.