I would rather see a study comparing country to country compared to USA vs the world. It looks more like cherry picking a rather small amount of cities chosen to make a broad statement.
I wouldn't exactly call it cherry picking, though it is a small sample size. I think the point is clear, on paper the US pays more for broadband. What isn't stated in the article is that most European countries have some form of Socialism and many industries are heavily subsidized. It's very difficult to accurately compare pricing without going deeper and seeing how far your paycheck goes.