Well if you’re calculating “the average American”, you have to include drug-addicted Americans.

If the mortality amongst drug addicts is moving the needle such that it's reflected in the national average, that means that drug addicts are average Americans.

Also, it's not just addicts who die from an overdose that is contributing to this effect. A hidden/functional addict is still going to die sooner on average than a non addict.

Average is not the same as typical.