I've got this impression too, you're not alone. I think one reason it might be that way is because of American culture. Americans stereotypically love to share

I've got this impression too, you're not alone. I think one reason it might be that way is because of American culture. Americans stereotypically love to share their thoughts and opinions, even unprompted with strangers. It might be that mentally ill Americans simply share more of their mental illness-influensed thoughts with the world, while people from other places deal with their mental illness more privately, like they're used to doing with normal thoughts. The other comments here are also likely accurate, America probably also simply has more people with untreated mental health issues due to their laws and their (lacking) health care system.