So, the $1.3 bn border plan that was already agreed last year on December 17?

Not quite.

Apart from several additions, the fold from Canada comes from moving their hazy plan phases from planning to implementing. That's where the W is for Trump.

It's a subtle difference. But with the addition of a temporary delay on the tariffs, Trudeau will actually be pressured into having to implement this thing. It's been a month and half since the plan was announced, and any Canadian that dislikes Trudeau knows he's not famous for actually doing something about issues that their own citizens ask for, even less other countries, so this would seem as necessary

Beyond that, 77% of Canada exports are to the US. That 77% makes up about 12% of the US total imports. I don't know what the endgame is but propping up Canada for a trade war they can't win is not the way.

Same as with Mexico. They are very conscious that many South American countries would like to step in their place should they fail to provide USA amicable trade relationship.

Up to you to make your own conjecture.