The US mobile market is by far the most dominant right now in terms of revenues and innovation across the stack. It wasn’t always like that. After inventing the industry, US lost the initiative to Japan and Europe until 2006–7 when the confluence of the iPhone, broadband networks, and robust applications ecosystem tilted things towards the US. Ever since, the US market has been on a rampage. And mobile data has been fueling this resurgence. In 2002, the mobile data market was approximately $1B. In 2014, US will become the first nation to cross the $100B mark in mobile data revenues. The next two nations are China and Japan, which are quite a bit behind. Having a 22% share of the data revenues gives US quite a bit of leverage over the ecosystem.
Tons of tidbits in that link.