Whatsapp is preinstalled on every phone you buy here (including iPhones, AFAIK, but maybe that's a sync thing? I don't know, I haven't seen an iPhone in ages). So it's pretty comparable these days.
For what it's worth, the timeline shift isn't just due to the SMS pricing changes. I think the general introduction of mobile telephony was also pretty staggered. I remember US-based media depicting the idea of a teen having long SMS conversations before I or anybody I knew had a feature phone. MSN dominance wasn't caused by expensive text messaging, it predates text messaging altogether, at least for mainstream users.
SMS is definitely a solid fallback for emergency services, though. It definitely retains use, even if it's mostly notifications from governments and companies.