In the past, the US has won wars in part by attacking the enemy's infrastructure. However, al Qaeda and the Taliban do not have much in the way of buildings and roads. But they do get a lot of funding through the production and sale of illegal drugs. If people were able to obtain drugs legally, depriving the terrorists' of their monopoly/cash cow.
Is this country willing to legalize drugs to win the War on Terror? Think of all the drastic measures this nation took in prior conflicts: the draft, the Manhattan Project, food rationing. During World War II, Ford and GM stopped making new cars in order to save vital resources. Can you imagine Congress or the President asking these two companies to cease production today? The legalization of drugs would be a far lesser strain on our way of life than any of these.