It's working in a way:
A survey of 17 countries has found that despite its punitive drug policies the United States has the highest levels of illegal cocaine and cannabis use. The authors found that 16.2% of people in the United States had used cocaine in their lifetime, a level much higher than any other country surveyed (the second highest level of cocaine use was in New Zealand, where 4.3% of people reported having used cocaine). Cannabis use was highest in the US (42.4%), followed by New Zealand (41.9%).
And the high drug use becomes the reason to keep at it. Perfect if you like endless war - and Washington clearly does. It's more powerful that way.