Right after Google got the green light to acquire Admob, the mobile advertising company today released a report analyzing where the majority of Android and iPhone operating systems are in its network around the world.

While the study notes that 75 percent of Android OS devices are in North America, compared to 49 percent of iPhone OS devices, the reality is that the iPhone still outnumbers Android two to one in the U.S. There were 8.7 million Android OS devices and 10.7 iPhone OS devices in the U.S. in April. Globally, the numbers are 11.6 million and 27.4 million, respectively.

While the total number of devices running the iPhone operating system may outnumber Android, a recent report from The NDP Group, an analytics firm, underscored that Android has passed iPhone is sales for the first quarter in 2010. So while there may still be more iPhone OS devices in the U.S., that soon could change as Android continues its sales growth. The NPD Group compiles and analyzes mobile device sales data based on more than 150,000 completed online consumer research surveys each month.

Admob’s last report looked at the newly launched Google phone, the Nexus One. While many thought it would rival the iPhone, the device only landed one in 50 mobile ad requests.

Admob serves mobile advertisements to some 23,000 mobile web sites and applications. Each month, the company analyzes the data from these ads to provide insight into what may be happening in the mobile industry.

A full report can be found here.