As far as I know opium was also sold and consumed in countries like Britain
I've covered dimensions of this in a number of past answers, which I will link below. If we want to be rather constructivist about it, opium caused problems because it was perceived as causing problems, and China was the site of especial moral panic over opium that was not as substantial (though far from nonexistent) elsewhere. There is also an extent to which China was a uniquely large-scale consumer of opium, although it's worth considering how other opiates, particularly morphine and heroin, have seen use, and consequent negative reaction, in the West.
https://www.reddit.com/r/AskHistorians/comments/ijja7c/how_true_is_this_vice_video_on_opium/g3jvv2y/