Seen from my window, Whatsapp gained traction as free international messages and voice - which are only attractive for usage across international boundaries, which is uncommon in the USA... Maybe that partly explains why SMS lasted longer in the USA.

Did it? My recollection was that it was more due to the wider usage of prepay, at least in my country. With more prepay, there were more people paying per message for SMS so once data got low enough people first went to IM clients (MSN, Facebook Messenger), then to the new wave of phone apps (Viber, Line, Whatsapp) of which Whatsapp was the eventual winner in the local market.

Accounts with per SMS billing were unlikely to have mobile data for comfortable Whatsapp usage, so I doubt that was the substitution.

To call between France and various African countries in the early Android era, I remember first using Viber - but after a while everyone switched to Whatsapp in a few months: somehow, through some sheer black magic, Whatsapp had nailed voice quality over the lossy high-latency links that were the norms then, and users noticed.

> Accounts with per SMS billing were unlikely to have mobile data for comfortable Whatsapp usage, so I doubt that was the substitution.

Care to quantify that? PAYG SMS was/is consistently way more expensive than PAYG data[1] in every country I have visited; granted I haven't been to many countries, but I've visited most continents. IIRC, there's a 2-3 orders of magnitude difference in the costs-per-140-bytes sent.

Per WhatsApp message, which ends up being a few KiB per day for text only

At the time of the rise of Viber and then Whatsapp, for people in Africa or communicating with Africa the messaging substitution wasn't an important question at all: we were burning so much money with international calls (and SMS) that any other tradeoff was a rounding error.

In the window where Viber then Whatsapp took off in my country it was €1 for 200mb of data on prepay but €0.15 per SMS. So if you sent more than 7-8 texts in the day the data was cheaper, and I think MMS were like €0.60 each.

Can't say people, to this day, have much of a culture of using whatsapp video calls. Skype was the majority in the Whatsapp takeover time and today it's a mix of Zoom and Skype. International calls also weren't that common.

So sounds like there may have been different motivations in your country than mine.

> Accounts with per SMS billing were unlikely to have mobile data for comfortable Whatsapp usage, so I doubt that was the substitution.

But I could jump onto coffee shop WiFi to negate that.

SMS are not always free, even locally. They are not convenient for a group chat. Apps allow group communication and is "free" over wifi.

The US has had stupidly overpriced cellular data, while unlimited texts have been a standard thing since like 2005 on even the cheapest plans.

SMS was more reliable for delivery with poor cellular connections, and many people learned to use it for that reason. The US (had) many rural areas with poor reception. So maybe that plays into it?

That theory would seem disproved by Mexico which is also pretty rural, but I believe their cell infrastructure sprung up pretty quickly and later than the US so "old school" sms didn't get the same traction.

US historically was much more into "unlimited" plans vs pay-per-use was/is more of a common thing in poorer countries. That may explain the prevalence of SMS in the US.