Not wireless, but broadband:

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.