The number of devices in the United States running Google’s Android operating system is closing in on the number of iPhones in the country, according to AdMob’s April 2010 Mobile Metrics Report (PDF LInk). As of April, AdMob saw requests from 10.7 million unique iPhones, compared to 8.7 million Android devices. When the iPhone, iPad, and iPod touch are taken together, they amount to 18.3 million devices. The situation is not the same worldwide, however. Globally, AdMob saw requests from 11.6 million unique Android devices, compared to 27.4 million iPhones. Again, when the iPhone, iPad, and iPod touch are taken together, this number is much higher—40.8 million globally. Overall, only 44% of iPhone OS requests are from the U.S, compared to 75% for Android. AdMob’s metrics are based on its advertising network of more than 23,000 mobile websites and applications around the world.