Can I play Pokemon Go in a country that I am visiting?

I'm from the United States and I'll be visiting Canada soon. Since Pokémon GO is not out for Canada yet, would I still be able to play and catch Pokémon in Canada seeing as my phone/game/account all originate from the United States?

For that matter, will I be able to play Pokémon GO in Canada once it is released in Canada? Or am I restricted to playing in the United States only?

You can only play Pokemon GO if the server allows you to play from the country you are visiting, as evidenced by this incident involving an Australian expat who visited Singapore and wasn't able to play Pokemon GO. They seem to allow/block based on IP address geolocation, since there is an article with instructions to use VPN to workaround the block.

Since there had been reports about people in Europe being able to play the game before the game is officially supported, the server evidently allows many countries beyond countries officially supported.

You can check the list of supported countries on releases.com, or follow the news and social media to see whether the game is supported in a particular country.

The game field is global. You can play it all over the world. This is both evidential from Ingress and the current Pokemon GO user base who play it globally at the moment with downloaded APKs.

Japan is in the testing phase so you can walk around all you want but you aren't gonna get any Pokemons popping up. I walked all ard Shinjuku and Hakone with no luck.