Here's why Europe is suspicious of Google's Android

An employee demonstrates a Motorola Moto E Android smartphone in the Lenovo pavilion at the Mobile World Congress in Barcelona, Spain, on March 3, 2015.
Simon Dawson | Bloomberg | Getty Images
An employee demonstrates a Motorola Moto E Android smartphone in the Lenovo pavilion at the Mobile World Congress in Barcelona, Spain, on March 3, 2015.

The antitrust allegations brought against Google by the European Union on Wednesday focused on the company's search engine business.

But the EU also announced an investigation into the company's Android mobile operating system. The OS itself is open source and free, but the included Google Play Store drives much of the growth in the company's "other revenues" segment. Android's rapid takeover of Europe has been striking.

In an internal memo responding to the EU announcement obtained by Re/code, Google said that while some Google apps come preloaded on Android devices, the OS often comes with competing apps such as Facebook while other apps are readily available through the Play Store.

"All told, consumers have a lot of choice, and they are exercising it," read the memo. "And many, many other companies have very successful mobile businesses—including Apple, the most valuable (mobile) company in the world."

Google acquired Android in 2005, and it quickly displaced competitors as the most popular mobile OS in Europe. Apple's iOS is still leading in the U.S., but in Europe, its market share looks far less impressive.