Non-US companies must use a EU-owned servers (not just EU servers controlled by AWS, DigitalOcean) to process EU data subject traffic. If they don't, they're in violation of Schrems II, which makes them in violation of the GDPR.
This is even more relevant as US data protection seems to only apply to US subjects - so an American using an EU service using a US host would be protected by US law (in theory, though likely not in practice), while an EU citizen using the same EU service is not protected by US law.
Is there a specific ruling or case that says AWS as a provider, regardless of where the actual data processing happens, is prohibited, this out that you can point me to?
More EU member states will likely follow.