My second-hand experience of developing countries is that almost everyone there at least wants to know English. I think Americans are actually the least likely to want to learn a second language, though non-Anglo developed countries probably have higher rates of successful bilingualism.

Probably not as off as you think. (And “education that offers second language courses” isn't the only way to learn another language. I'd guess there are lots of (say) people living in mixed-ethnicities zones, or people who live in places other than they grew up in, who pick up other languages without formal study. You know, outside North America it's not that common to travel a thousand miles and find that everyone still speaks the same language.)

ETA: and “education that offers second language courses” is way overrated anyway. In Italy and Ireland at least, most people made to study a second language during compulsory schooling don't attain anything remotely resembling usable fluency (I mean, they can't even get the gist of news on TV), and those who do usually have exposed themselves to lots of second-language media for non-school-related reasons.

No, humans living in very poor countries or in remote past also always tried to have at least basic understanding of neighbouring tribe's language. It's hard to come with hard data but modern nation states might probably be about the only large monolingual societies in history, other than small and very isolated places.

In modern Africa it's entirely normal for people to speak 3+ languages. (not necessarily to a very high standard, just to get by)