I have noticed that President Trump first gives a warning.
The warning was given and ignored. The Mexican Government half hearted attempt to slow the invading army was nothing more then Kubuki theater.
He just put more force in his warning. Declaring a National Emergency is the key phase. Putting our military on alert is him picking up the big stick although the real punishment will be cutting off all funds to the countries involved.
The President has shown a willing to negotiate, what he does not do is bluff.
Mexico the ball is in your court. You are going to be a good neighbor or the President will punish you.
A situation like this has a process of escalation so that all of your bases are covered.
Morons on our side think that we should be sending in air strikes, invading countries, jailing politicians, and otherwise annexed parts of Mexico and turned them into no-man lands, with so far none of that horde anywhere near the border.
Because they are bored apparently.
That's a real nice trade deal we just negotiated with you. It'd be a shame if we had to cancel it.