You can add India to the list. WhatsApp is so popular here that people talk of recharging WhatsApp when they actually mean paying their mobile internet bill.
Africa runs on WhatsApp (atleast, West Africa, Kenya, Uganda, Egypt, Tanzania...) IME.
As an Australian, is this true? Granted, I grew up rural in Victoria, but I don't know anyone who uses it.
It's definitely not true for Australia. WhatsApp use is marginal at best.