That is definitely not the case. They will always find a way. Even the best case scenario we have here has cut down ILLEGAL crossings 95%. That's considerable, but that still leaves 5%. I have been on the freeway in South Bay and seen hordes of ILLEGALs as they rushed the border at once. No fencing can stop that. They'll run through traffic, cross lanes leaping over cars that have stopped to avoid them. They'll do what they have to do to get away. There's always a way.
The tunnel's aren't an issue as far as ILLEGALs go. Those are usually for drug smuggling. And w/o the fencing they just drive the drugs across. WHy not erect the fencing and make them dig the tunnels?
The fencing has made my home safer. I live incredibly close to the US/Mexico border. There was a time when ILLEGALS crossed through my property regularly. They picked fruit from my trees. They filled their water jugs with my hose, broke into my garage and other buildings, tried to break into and hotwire my vehicles and even tried to steal my elderly neighbor's car. Fortunately she was armed and defended herself. That all ended with the erection of the new fencing. So obviously I am a big proponent of fencing. I know it works as I have seen its benefits first hand.
Put a 10% tax on wire transfers to Mexico to fund construction. Reduce the tax to 2% to pay for maintenance when the wall is complete.
Remember what we learned from Obamacare - a program with a dedicated funding source can’t be repealed through the annual appropriations process.