Also, the article isn't really about the US. The question about the correlation (the HN title is the subhead; the title is "What performance-enhancing stimulant

Also, the article isn't really about the US. The question about the correlation (the HN title is the subhead; the title is "What performance-enhancing stimulants mean for economic growth") isn't the main topic of the article, but a framing device for discussing the idea that availability of stimulants contributed to the industrial and scientific progress of Europe and the UK in the 19th century.