I think it's more a perception because America is more progressive about mental health care than most countries (maybe thanks to big pharma, I don't know though

I think it's more a perception because America is more progressive about mental health care than most countries (maybe thanks to big pharma, I don't know though). It's extremely likely for ADHD to be under-reported in other countries because of the lack of screening for this sort of thing. In my experience in other countries, the primary difficulty for ADHD support groups is that many country's medical institutions do not even acknowledge ADHD as a thing. Some of these institutions acknowledge, but seem to believe that the condition disappears when you turn 18. Many of the regulatory institutions don't allow stimulants to be used for treatment, either. This is mostly an anti-scientific position. ADHD is extremely well-researched. Its (medication-based, not CBT) treatment is the most effective of any mental illness, more so than "understood" things like depression. I'm biased, but I think a lot of places are still in denial about ADHD. There's way too much research around the illness and its effects and treatment.