One of my friends at Carleton wrote her senior thesis on the tension between America's counter-insurgency tactics in Afghanistan, and our counter-narcotics tactics there. It was a good argument that I think deserves greater attention (I say that while I'm sure I'm not doing it full justice).
The link between the drug war and the war on terror is no mystery. Terrorists like drug money because its already an underground economy, so the transfer paths are already present in ways designed not to alert the authorities. But fighting the drug war makes allies of the terrorists and the drug producers -- the cartels, yes, but also the peasant population which grow the crops as their primary source of income.
This creates a problem. Basically, America's standard counter-insurgency operations revolve around the "winning hearts and minds" cliche. We try and stabilize regions, build institutions, increase the well-being of the locals, and help them get their goods to the market. If they like us, or even if they just are content with the status quo, the support for the insurgency withers away. Win for Team America.
Our counter-narcotics operations, by contrast, are based on eradication. We go in, and destroy the poppy crops. This means that our first exposure to many Afghan families is decimating their livelihoods, which is a problem on the whole hearts-and-minds metric. More specifically, rather than seeing Americans as a source for enhanced stability or a brighter future, locals instead rationally conclude that the only way to keep their crops safe is to insure that America or the central Afghan government doesn't get near them. That makes support for the insurgents skyrocket. And the insurgents reciprocate by protecting and promoting poppy cultivation. This dynamic has made it nearly impossible for anti-Taliban forces to crack the Taliban's hold on Southern Afghanistan, which, in addition to being their original base of support, is also a prime poppy region. The insistence on fighting the drug war in this way is making it impossible for the army -- and the Afghanistan government -- to do its job: unite the country, and stifle the insurgency.