I wonder why so many people think it is impossible to build walls practically impenetrable?
For four allmost decades we had an "wall" surrounding East Germany that very few ever succeeded to cross - and that was even with East German technology and zeal. In this case is not significant what the most creative fraction of a percent can do, but what the 99+% are capable of.
Technology etc. is present, the main requirement is will. Right now that will is limited but rising on a parallel curve with illegal immigration. Just wait and people will vote for minefields and high voltage etc. although you probably don't need all the bloody devices to make it "safe". And as the problem get distant in time, the walls will be dismantled again, and next something entirely differnt is oin the agenda...
But large demographic reloactions always in the history of mankind has caused great turmoil, why on earth shouldn't it do this time?
And if the Americans need housekeepers and gardeners, why don't just deal out some green cards in the number needed?
Regards
Steffen Redbeard