Is Difference Between German and English Versions Possible?
Yes, it is possible. There can be several reasons. For example, most visitors from the US may use certain devices, browsers, etc., that German visitors may use sparingly. Server location, DNS speed, etc., may play a part. You have to segment the visitors from the US and Germany and profile them to start analyzing.
Note:
Google's core web vitals update didn't happen in May. The page experience update started on June 16 (https://twitter.com/googlesearchc/status/1404886100087246848) and is in progress. The update is expected to be completed by August.