I used to live in San Diego and made the drive back and forth more times than I wanted. The majority of the land from the Pacific Ocean to El Paso is flat and desert-like, and thus fairly easy land to drop a Wall. Texas has some of that too, but also has areas where a Wall is not practical, like Big Bend. But I've never seen the problem with that. At worse, the illegal entries would be funneled into limited entry points and thus easier to collect. BP might only have to worry about 200 miles instead of 2,000. Think of the manpower that would save.
Likewise with the idea of tunnels, if that is what you meant. Tunnels are very expensive and take time to dig and construct. This is why only narcos build them -- no one else can afford it. If they want to keep investing in them, then fine. Go for it. We get better at detecting them every day.
I am also against the federal govt avoiding its responsibility to protect the national borders and sliding this burden onto employers. They are already burdened with collecting the FUTA, FICA and health premiums. Not to mention OSHA and EPA rules, or state, county and city regulations. Enough already. Small business owners are the #1 new job creators in the US. They deserve so much better than they get. Moreover, guarding the national boundary is one of the core responsibilities of national govts around the world. Without this, there is no need for a federal govt. Indeed, you have no nation at all. How about instead we pull the US Army out of Afghanistan and put them on the Southern border? It would be cheaper for us, and safer for them.
The "make employers do it" idea is actually a part of the latest amnesty proposal with a misleadingly dumb name. This one is called the "New Way Forward Act." This one --
—Decriminalizes illegal entry
—Eliminates the deportation of criminal illegals
—Cripples ICE enforcement
—Forces taxpayers to fund illegals’ re-entry into the US
This is the proponent Democrats’ vision for the US.
Here is Tucker Carlson addressing that proposed federal law --