The EU has recently created a Digital COVID certificate so that EU-members and non-EU members can travel throughout the EU

The EU has recently created a Digital COVID certificate so that EU-members and non-EU members can travel throughout the EU. Upon review of the non-EU members that have agreed to participate in the EU Digital COVID Certificate program, you will note that the U.S. is not a signatory. The protection of personal data is described in Article 9 of the enabling EU Regulation.

Consider the current legal protections for the protection of individual personal data in the U.S. when answering the following questions. What would be the legal rationale underlying the U.S. to not be signatory as a non-EU member to the EU Digital COVID Certificate? Consider any differences between the EU and US approaches to individual privacy as well as any other potential obstacles for either the EU or US when responding to this Thread.