But again, what if they call his bluff. What does Trump do then? Because "solving the border crisis by requiring Mexico to pay for the wall" didn't work last time, and they are coming to the table with a much better plan this time.
Keep in mind, Trump plays a very short game (it's why he gets a diplomacy handicap). He just has to look like a winner until he dies. That's his aim. Countries like Mexico and Canada simply aren't interested in encouraging bad behavior from their already volatile sibling.