In the English language "America" typically refers to the US because Anglos don't pretend North and South America are a single continent while separating Europe and Asia. There's no ambiguity when someone says "America".
It's comparable to saying "In Britain they speak English". This is correct enough for a sports bar but reveals ignorance of what the words "Britain" or "English" mean, plus a certain disregard for cultures.
But WhatsApp is the dominant messaging platform in most of the world. E.g. in the UK it has basically 100% market share.