Is this mainly a US-centric take though? In the UK, yes we had AOL here and a fair number of people I knew had it, but it was never dominant as far as I could tell (I’d be happy to be corrected, I only came in around 1997). It was MSN messenger that became established as the dominant instant messenger here by about 2000, I don’t really remember too many people using AIM.
Yes, the differences are fascinating, I know Minitel was big in France. To my mind it was Freeserve that brought the internet to the masses in the UK (and spawned many dozens of similar ISPs in the late-90s), but seems to be a bit of a footnote now. My peers first started messaging through YIM (Yahoo! Instant Messenger) before MSN took over as the default. I remember AOL was perceived as an expensive ISP which limited the popularity of AIM.