I'm still not convinced. Wouldn't destroying the canal make every other country in the world hate them forever? (Except Chile, who would be overjoyed)
It seems like one of the riskiest possible diplomatic moves, especially if they're going to try afterward to pretend to play within the international system and find a way to blame the US (false flag, etc) for starting the nuclear war.
Panama was strategically important target. Russians wouldn't be idiots if they wouldn't do that. And I don't think that Soviets much cared about that what else would think.