GDPR does not care about where your servers are located.
It seems to be in certain cases. For example Meta is subject to GDPR because they have EU headquarters, and were subject to fines because they transferred EU data to US servers.
If they have headquarters outside the EU, and only use data they've already acquired/processed to make money off of EU consumers from outside the EU, GDPR shouldn't be an issue for them in the same way.
And GDPR makes it harder for their competitors to catch up because it's harder for those competitors to get data.
Aren't they subject to GDPR because they do business in the EU with EU citizens? I don't see how that would change.
Probably, but not in the same way. I'm guessing they wouldn't have been fined for external data transfers if their servers were located outside the EU.
It could be that the EU would block them if they wanted to host fb/etc... including ads, and didn't have a presence in the EU, but I'm not sure if that's the case.