ClickZ recently posted a great article by Laura Marriott, the executive director of the Mobile Marketing Association. You can read it here.
In a nutshell, she raises the question of how far behind the United States might be from Europe in terms of mobile marketing. While she doesn't suggest there should be a simple answer, her anecdotes paint a picture of a U.S. that isn't too far behind at all.
In the end, it will come down to consumers who actively use the data services of mobile phones. On a per-capita basis, the U.S. definitely trails Europe and Asia. But Laura makes a great point that we are catching up quickly.
However, I think the real story here is that mobile marketing may be one of the first truly global marketing channels. Even more so than the Internet in some ways, handsets and airwaves can level the marketing playing field for truly global marketers like nothing before.