We know absolutely why the anti-opium laws were passed; there's no mystery here.
It was to enable the government to deport unwanted Chinese laborers back to China.
the same sorts of laws were enacted in Canada prior to your Harrison Act.
Similarly, the laws against marijuana, in Canada, were specifically aimed at black jazz musicians--you could look it up. Apparently, your anti-marijuana laws were anti-Mexican.
How any moral person can associate themselves with the devilish indecency of these laws is beyond me.
(Actually, that's not true--I know it's peer pressure...and pensions.)
Do read more factual history, dear. It wasn't only because of Chinese immigrants, that opiates were made illegal in the USA. As a matter of fact, specifically read up on laudanum. It was the cause of many unintentional and intentional infanticides in the USA, England, and everywhere else it was legally sold. Opiates were also a major ingredient in many patent medicines, as were heroin, cocaine, and alcohol.
Unlike today, most addicts, of 100 years ago, were the dregs of society ... whores, actresses, actors, dillitants, and bums. It wasn't race, it was degeneracy. The high end mistresses of the Demi Monde, used laudanum to attempt suicide or as a scare tactic ( for their lovers ) to keep / get back a rich patron. Teens weren't doing any form of dope, for the heck of it.