Put some of the military on the border. Consider it an invasion and repel it by all means necessary. Mines, M-60s, and pull up a few P 47s out of mothballs for strafing (worked in Ger in WW2).
They didn’t build a wall, because they supported amnesty.
Did you notice the photographs of the response at the Ft. Lauderdale airport mass-shooting?
Military outfitted men and vehicles poured in within minutes, by the hundreds. They have fleets of shiny new expensive SUV’s, trucks, and sedans and all the finest equipment. Between NSA, DHS, ATF and whomever else responded, it was massive.
We already have the resources and the means to do this.