Fences will work.......
IF EVER THEY ARE TRIED!!!!!!!!!!!!
I'm not against fences but I think you're wrong.
As long as we give free health and education and all other bennies to illegals, and then prohibit local LEOs from doing basic law enforcement regarding them we are going to continue to have a permanent and, ultimately, destructive illegal problem regardless of how high a fence we build.
OTOH, if you end free bennies and let local LEOs do their work, you will not need a fence or a 2,000-mile long one anyway.