Libertarian cow : Abattoirs were originally for the treatment of sick cows not the wholesale slaughter for meat they have become.
Libertarian human : Governments were originally for the protection of the people not the corrupt special interests.
In Empires of the Silk Road the author maintains that the internal economic collapse of the Roman Empire not only allowed the 'barbarian' invasions but caused them indirectly. Since the Eurasian tribes depended on trade with the Romans, the failure of the Roman economy led to a failure of the tribal economies also. This gave them an incentive to uproot and invade Roman territory at the exact time Rome was weak. Since it already seems likely that Roman economic collapse was caused by the centralisation and militarisation of the economy by Imperial decrees, it follows that this economic mismanagement in the name of military strength caused military disaster too.
Riffing on this we can speculate that the collapse of the US economy will not cause the Mexicans to leave as some anti-immigrant thinkers wish. In fact Mexico's economy might collapse even further than America's and cause more Mexicans to flood in. Since the south of border area is already awash with armed bands due to the war on drugs there will be plenty of guns to attack US officials attempting to stem this tide. The neo-cons will finally have a nice little war close to home. Naturally this will lead to paranoid claims that the Spanish wish to destroy our English freedoms and the only solution is to nuke Mexico City and Madrid.