The awaited release of Pokemon GO has begun, however, at current, only two countries have access to it: New Zealand and Australia. Other regions, via posts on Twitter, have stated they can’t find the app on their android and iOS devices. Meaning that a full worldwise release has not occurred yet.
Nintendo has not made a statement about the region release, but it’s very likely one will occur soon. It was stated at E3 by Shigeru Miyamoto that Pokemon GO would release in July, but he did not state that it would be a worldwide universal release. Potentially, Nintendo is segmenting the launch to ensure no major bugs are found upon launch before releasing into the major territories.