> If no data about user A is allowed to be stored in the USA, the server in the USA can not know who A is IANAL, but to my best knowledge, holding one-off data

> If no data about user A is allowed to be stored in the USA, the server in the USA can not know who A is IANAL, but to my best knowledge, holding one-off data in memory is repeatedly defended in European courts as not storing data. This is from the top of my head, so treat it as "probably wrong". All in all, the whole thing is a bit of a circus, really.