I am in US, from an Asian community; & people in my circle who own an iPhone still prefer Whatsapp for like 100+ msgs a day. Never saw them using iMessage even for other iPhone users.
Which is surprising considering how bad it is.
In what way is iMessage bad? It works amazingly well from my perspective.
And you're using an android phone I presume?
WhatsApp runs the exact same whether it's an iPhone or an android phone. That's not trivial.
iMessage when I have to use my MacBook because my phone is charging is amazingly awful, completely inflexible.