The War on Drugs is not about stopping the flow of drugs. It is about injecting an industry and bureaucracy into an existing market.
The international drug trade is a $400 billion a year industry. That is no street peddler level money, that is serious business, and that isn't even counting the tax dollars funneled into huge government agencies, prison systems, law enforcement agencies, advertising programs, etc.
The "War on Drugs" in the US acts as a macroeconomic mechanism to export USD to other countries. The War on Drugs drives up drug prices, which greatly increases the amount of USD exported.
This is very similar to how USD are used in oil transactions - it artificially increases demand for USD outside the US.
And now Bitcoin may become a larger part of the drug trade, it's likely to increase demand for Bitcoin in a similar fashion. However, Bitcoin is not as anonymous as cash (due to public ledger). But this can be solved using mixers and alternative currencies.