Earlier quoted context omitted.
The justification is Trump wants to do to Canada much what Putin is doing to Ukraine. Russia being allowed to take Ukraine legitimizes world powers engaging in conquest within their sphere. It's really that simple. The talk about fentanyl, the supposed trade imbalance, and all the rest is just smoke and noise, because if he said that he wanted to raid Canada for resources and Lebensraum it might actually threaten his…
It is worse than this. Trump is just the spokesman for a younger group who is steering him. He doesn't actually know anything, he's just being fed punchlines and he's good at regurgitating them.
This was a major thing in his first term. People fight to be the last person to speak in a meeting.