Such as? (I'm sure you corrected for population density)
http://www.engadget.com/2011/06/28/why-is-european-broadband...
Meanwhile, the size of the U.S. may be a red herring. Most of the region between Boston and Washington is as densely populated as most of Europe and the UK. So is the California coast between San Francisco and San Diego. And so is the region of the Midwest centered on Chicago. Those areas are home to about a quarter of all Americans. In other words, we live in a big country, but a lot of it is relatively empty space.
The article makes several other oversights. First, the big US carriers do not have regional pricing, and so the population density of the entire country is relevant.
Second, it neglects to mention that CDMA deployment was forbidden by law in many EU countries.
Finally, it neglects to mention that NIMBYism is a major driver of cellular network cost in the US, and differences in the legal climate around tower deployment can account for large differences in costs.
Isn't wikipedia great?