I have reveiced hundreds questions about downloading Clash Royale since last night.
Currently, only players from these countries can download Clash Royale from the iOS App Store: Denmark, Finland, Hong Kong, Canada, Australia, Norway, Sweden, Iceland and New Zealand. However, there is still a way to bypass this limit.
By changing the country of your iTunes Store account to one of those mentioned countries above, you can easily find and download this game. For more details of the step-by-steps tutorial, please take a look at here.
Enjoy the game!