AdMob’s January traffic analysis credits Apple with a majority share of the American smartphone market and notes the iPod touch is rapidly gaining ground as well.

The ad company’s latest Mobile Metrics report, which tracks handheld web traffic based on served banner and text ads, gives the iPhone a majority 51 percent share of smartphone requests handled in the United States despite the Apple device’s official limitation to a single carrier.

In view of the entire U.S. handset market, of which smartphones represent a smaller growing sector, Apple devices left their competitors behind and trumped Motorola by almost 10 percent. Should this shock people? Not really…the iPhone has been the smartphone’s most hyped big brother for awhile now.

The iPhone maker was the only firm to post a percentage gain greater than a half-point, and ultimately saw 6 percent growth where most stayed near-flat or declined. A breakdown by each particular device shows the iPhone making almost 17 percent of all mobile web requests in the United States, while the iPod touch requested a still-large 12.3 percent.

That means the iPod touch, likely reflecting the holiday season’s record sales of iPods, upped its market share by 5.2 percent in January, besting all others by almost 5 percentage points.