However, according to a relatively recent European Court of Justice ruling you're not allowed to transfer any personally identifiable information to companies that are in any way affiliated with a US-based entity (e.g., by virtue of having a US-based parent company) anymore. Just being physically located in the EU isn't sufficient according to this ruling.
The reason for this is that with FISA US law enforcement can force US-based companies to hand over any data, even if that data is stored with an international subsidiary under a completely different jurisdiction.
This basically invalidates all of the provisions and legal frameworks for interacting with non-EU entities that used to be acceptable under GDPR before (e.g., Privacy Shield).
However, not interacting with any US-based or US-related entities at all anymore would be tantamount to ceasing almost all economic activity. So, until (or more pessimistically: unless) the US and the EU come to terms on a new agreement regarding privacy rules, there probably isn't anything a business can do on its own to completely address this issue. At this point, merely hosting data on servers physically located in the EU perhaps amounts to little more than window dressing.
Realistically, as of now your best option probably is to continue to put in your best effort to protect customer data (which might include hosting data exclusively in the EU) and document everything in the process.