On June 20, 2019, Niantic released Harry Potter: Wizards Unite to the US and UK regions. This was ahead of the original announcement that said the game would release on June 21st.
Multiple sources have come forward to say that the rest of the world can expect to get into the wizarding world tomorrow, June 21st!
It is worth noting that the Pokemon GO initial release was a staged rollout that lasted multiple days across the world. Pokemon GO originally rolled out in the EU rom July 13th to 17th, with its initial release in Australia, New Zealand, and the US happening a week earlier on July 8th.
If you're preparing for the worldwide release of the game, check out our guides on our Wizards Unite site! We have all the information you're looking for.