Is that the comment of someone who is looking to negotiate? Especially after HE walked away from the deal his negotiators brokered and accepted?

This plays well to the Canadian faction that has been simmering in anti American sentiment for a while being fed to them by their media.
For the PM of Canada to claim that they are at war with the US marks a new level of escalation - particularly since his own negotiators felt it was a reasonable deal and agreed to it before Carney stepped in.
Carney never meant to sign any deal. he is not working in the best interest of Canadians. He is also doing the same thing to the Canadian economy that he did to the UK banking system before they got rid of him.
Canada at this point is all in on getting rid of Trump, but here is the thing: these tariffs are controlled completely, and legally by the POTUS this time around. The Midterm Elections will not change them.
Thus, while Carney plays the longer game for his European Globalists to get the Dems back in charge to let the US gravy train restart, that cannot happen for at least 2 years which the Canadians cannot afford as even now they give govt subsidies to their businesses.
Industry will move back to the US (esp auto).
Canada is the sacrificial lamb for Carney's globalist play.