All EU companies sending any PII to US-owned companies, regardless if the actual data stays in the EU or not, are in danger to be sued similarly to the author of this post. This is, among other laws, because of the US CLOUD act:
> The CLOUD Act primarily amends the Stored Communications Act (SCA) of 1986 to allow federal law enforcement to compel U.S.-based technology companies via warrant or subpoena to provide requested data stored on servers regardless of whether the data are stored in the U.S. or on foreign soil.
> The CLOUD Act primarily amends the Stored Communications Act (SCA) of 1986 to allow federal law enforcement to compel U.S.-based technology companies via warrant or subpoena to provide requested data stored on servers regardless of whether the data are stored in the U.S. or on foreign soil.
So, it's not a Shopify specific issue.
https://en.wikipedia.org/wiki/CLOUD_Act