But, as these things go, regulation isn't that much about where you put the computers, but about where you register your company, and where your customers are living.
In terms of regulation, it depends on the specifics. Sometimes it depends on where the customer lives, but even if it does, when a platform has no business operations in a region and there aren't international treaties between the consumer country and where they're operating from to resolve that sort of thing, the most the regulating country can do is block them.
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.
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.
Where you put something is completely irrelevant.
Where you put something, like a data center, can be relevant. If Meta didn't have a business presence in the EU, and operated their data centers outside of the EU, they wouldn't have been subject to GDPR in the same way they were.