In 2010, Electronic Frontier Foundation launched a website where visitors can test their browser fingerprint.[14] After collecting a sample of 470161 fingerprints, they measured at least 18.1 bits of entropy possible from browser fingerprinting,[15] but that was before the advancements of canvas fingerprinting, which claims to add another 5.7 bits.
If I'm understanding that correctly, that would give ~14.6 million unique fingerprints just based on your browser. That's a lot, but also tiny compared to the billions of Meta users. I'm a little skeptical that they would be able to determine a user is from the EU without using IP or cookies.
Edit: If they block users who's fingerprint matches an EU user, and their IP comes from a known VPN service, then they could likely get pretty good accuracy. I wonder if there are any North Americans getting blocked while using a VPN.
There's only so much information you can get with hardware though. No doubt the software in tracking fingerprints, and matching similar ones has become very sophisticated. However, I wouldn't be surprised if device fingerprints hasnt increased in diversity much.
On the other hand, maybe they're using a spectre/meltdown attack to get a MAC address or something. In that case, we're fucked.