And what's the common theme ... drugs. The theory that people can be stopped from getting off their face by making certain substances illegal is proved incorrect yet again.
The battles in Mexico are all about controlling the drug routes into the US. It's a multi-billion dollar trade so wiping out one cartel merely creates a business opportunity for another. And just to spice things up a bit relations between the US and Mexico are souring fast. The US denounces the Mexicans as useless beaners who can't police their country or control their border; the Mexicans see the ceaseless thirst of US citizens for drugs as the cause of the problem, they think the US wants a porous border to provide cheap imported labour and they see that the guns used are all bought in the US.
And in Afghanistan we see that the single biggest part of the economy is drug money. What's the quickest way to the sea ? Pakistan.