Chain link fence. Dead zone with motion detection (can be designed such that digging is detected and also to produce few false positives). 20 foot wall with concrete shell and rammed earth center (to keep the cost down).
In remote areas relatively few towers would be needed as heli borne teams can respond to alarms. Around any population centers guard towers might be necessary depending on how good the motion detection systems are (they need to be designed both for seismic activity and for motion / infrared for above ground activity.
If you are caught in the country illegally - you spend six months hard labor working on the wall. If you are caught hiring illegals - you spend 6 months hard labor working on the wall.
The wall would not be necessary if we only had illegal workers coming in. Those can be stopped by shutting off employment and benefits. But, unfortunately, we have to deal with criminal and islamic incursion also. So we need a wall.
The muslims will then shift to the northern border. At that point additional measures will need to be taken. Like making islam illegal in the US.
Since all muslims (at least all sunni and shia) advocate for the imposition of sharia law over all countries - that makes them traitors to the constitution our government, and way of life. It makes them by definition traitors. And that makes it legal to make the practice of their ‘religion’ illegal.