President Donald Trump risks seriously damaging the relationship between Canada and the U.S. as he pushes toward a new North American Free Trade Agreement, former U.S. Ambassador to Canada Bruce Heyman told CNBC on Friday.

"The definition of insanity, just listening to the president there, is how the president has been treating Canada all this time. You know, this is our best trading partner in the world," Heyman said on CNBC's "Squawk on the Street."