You make a very fair point.
The drug war has been a total disaster. It's thrown much of Latin America into chaos, with their governments unable to contend with the sophistication and brutality of drug cartels that rake in billions from the most lucrative drug market in the world, the United States. It's also a massive source of revenue for the criminal gangs that plague our cities within our country.
The laughable propaganda from the government has also totally undermined important anti-drug messages. The ridiculous claims about the dangers of weed, for example. The reefer madness stuff. The DEA's insistence on keeping weed Schedule I. It's actually given rise to an equally ridiculous myth: that weed is totally harmless. But more importantly, it's undermined the message against harder drugs. If the government is lying about weed and shrooms, then people will think they're lying about other drugs as well.
If we don't win the cultural battle against drug use being acceptable, then all is lost. You're right that no amount of law enforcement can change that in a liberal democracy. But assuming that battle can be won, this is what I think needs to happen on the legal and military end:
I say legalize weed and other drugs with lower abuse potential; this will immediately destroy the largest segment of the illegal drug market. For hard drugs, stop imprisoning people for possession. Withhold the first arrest for simple possession from the public record, so it doesn't show up on background checks and destroy people's ability to get a job. This will create the public support for what must come next: come down like an iron fist on the weakened organized crime groups that have lost their largest source of revenue. Exploit internal strife caused by dwindling revenues, turn some people into informants, and then put away the rest for a very long time.
The second biggest drug market is cocaine. Almost all of it comes from Colombia. Once the current peace process falls through or fails to stick, the US needs to help Colombia finish off the FARC completely. Unconditional surrender should be the only acceptable outcome. A complete commitment to ending mass coca production in Colombia should then be a condition of their friendly standing with the United States.