Mexico is the US's ghetto and like a lot of ghettos in the US it's more cost effective to keep a wall around it and have the cops keep a close watch. It helps to raise property values outside the ghetto and contain the low lifes and riots.
No fuss over the Northern one - the citizens there like it there. Nobody plans to unify NA. My "brethren" learn my language and don't look at me like English is funny. :p
Hush. No one is supposed to know our plan. Don't make us hook up Google or Facebook to monitor your packets. Oh...I see you've already done that willingly. Y'all have a nice day. Go USA!