The US never stopped trafficking opium.
After WWII the US banned the growing of opium and cocaine, except by US approved growers. Most people today don’t realize that Indonesia was the worlds largest producer of cocaine. The Dutch East India company had huge plantations, and grew the strongest cocaine. After WWII the US forced the Netherlands to destroy the plantations.
The US only a few years back, threatened to revoke Australia’s right to grow opium. The US backed off, when they found out the opium farms were owned by Johnson&Johnson.
During the Vietnam war the US flooded SE Asia with opium, and Air America delivered it to the rest of the world. After the US defeat in Vietnam the opium growing was mostly stamped out.
Next the US chose Mexico to grow the opium, but that didn’t work out, so production moved to Afghanistan, under the control of the CIA, proceeds were used to fund the terror war against Russia. When the Russians were defeated, the CIA left, and the Taliban stamped out opium growing. The US invade Afghanistan, and flooded the world with opium.
Empires using drugs as a way of promoting political and financial interests is an old tactic.