There isn't much in fact. Most of the so-called civilized world still puts drug offenders in prison, a lot. Just take a look at Japan's extreme drug laws for example (they apparently don't count as civilized).

The parent is claiming a few, mostly tiny European nations represent the majority of all civilized nations.

Depending on what the word "civilized" is supposed to mean it could be true. Nations where the death penalty is still given are not considered civilized in Europe, so there's that. (But everyone chooses not to care in America's case :))

A lot of the developed world does not really enforce the laws on mere users. Certainly nowhere as strictly as it was enforced on inner-city african-americans.

Simple drug possession is one of those offences that is mostly used as a hammer to whack people who are "nuisances".