SMS used to be the standard way of messaging people on a cellphone. Since a European country is about the size of one US state, it's pretty common to have friends, family or other people you have to message in another European country. Many carriers still charge additional fees for sending SMS messages to other EU countries. So Europeans needed some way of messaging people in other countries for free. That's where WhatsApp came in, it's designed for phones and simpler to use than Email. In 2013, WhatsApp was bought by Facebook, which later became Meta. It's basically the same for other countries that rely on WhatsApp, they need to send messages to foreign countries frequently, which can become quite expensive when using SMS. Americans never needed WhatsApp, because they don't have to message people in foreign countries as often as Europeans, and they often have unlimited SMS included in their cell plans.