re: How hard is it to actually secure the border?

Start by deterrence. Once word spreads that you're in a detention center for 3+ months only to be deported immediately following the detention, it may deter a good portion of those willing to brave the desert. First time, 3 months. Second time caught, a year. Third time, shark tank.

As it stands now, come one come all and you'll be released into the community with a promise to appear? wtf.