By the time Facebook and Twitter were founded, about 2/3rds of the US was online: http://www.internetlivestats.com/internet-users/us/

So a) one didn't have to be hugely privileged to be online before social media took over, and b) I don't think the level of privilege of participants has much to do with the change that this article is talking about.

1. There are countries outside the US (and Europe)

2. Most of these countries came online only in the mobile era

3. Many of these countries have Facebook and broadly, Internet usage that eclipses US and Europe.

I don’t think they’ve been online long enough to have much relevance to the point of this article though.

I agree all those things are true, but I don't see how they are relevant to the point. Are you perhaps claiming that social media evolved differently in some of those countries and so one of them serves as some sort of contrasting example to the article?