What a dumb chart. It obviously left out data that wouldn't make its point: Canada, United Arab Emirates, Israel, Italy, ...
It may be a dumb map. But I think you might be able to draw correlation even if you take all countries into account.
Beyond that though, wow. I'm amazed that a poor article on something so far from Hacker News got upvoted so many times.
The correlation is -.80: that's amazing especially in contrast with where the U.S. stands.
Still, I agree that I'd love to see this data with every country included. But I highly doubt it would change the correlation that much.