5,000 military to the border.
How fast can the military build a military base with perimeter.
All they really need to do is build the perimeter.
How many miles of impassable perimeter can the military and it's engineers build in a few weeks or a month?
Also 2,000 national guard. Barb wire and electric fencing as the first line, then an open zone for apprehension, then a more fortified perimeter with electronic and personnel monitoring. If a mass charge use the repulsion non-lethal technology.
With that many hands and discipline and resources they can put up a mile of impassable perimeter a day.
Military has all the funding it needs. If sent to defend the border and defending the border requires a solid secure perimeter they have the authority to secure that perimeter - and if they want part of that to be a wall they can have it up in days at any location..
Electrified Cyclone barbed wire - will surely slow down a mob.
another question secondary to this one is:
Can it, and regular barb or razor wire be electrified?
in a good fort this would be the outside line with a dead man zone behind it and in front of the more fortified barrier.