SimilarWeb posted a study showing the most used chat apps per country. Take a look...
The study gathers data from all Android devices in almost 190 countries. As expected, WhatsApp is the winner of them all, though some interesting facts come out of this study. The USA and Canada have Facebook Messenger as its most used chat app, while some Eastern Europe and African countries use Viber. Line and Telegram have little popularity while WeChat is the #1 chat service in China.
As you can see, Facebook, which bought WhatsApp some time ago, dominates the world of smartphone messaging with its two applications. Overall, WhatsApp is the #1 service in 109 countries.
What about you? What's your main messaging app?