It can't be all there is to it. In Afghanistan, puppies have been cultivated in open fields for decades and the US hasn't done shit - besides patrolling. I remember reading somewhere that the US banks benefited from the liquid cash of these kind of activities during the financial crisis in 2008.

Puppies growing in open fields sounds adorable. But in all seriousness, no those activities do not generate "liquid cash" (if anything they're more likely to use physical cash as storage and withdraw it from circulation) and even if there was a plausible mechanism by which it could help US banks, the size of it is very small potatoes compared to the woes encountered in 2008.

Since I am not an economist, I can't argue its validity:

http://www.reuters.com/article/financial-un-drugs-idUSLP6507...