I often get automated emails about unwanted registrations to some review websites and asking me to review for random, typically paywalled journals. Is there any to stop or reduce that kind of spam?
Example of such emails with the paywalled Displays journal published by Elsevier:
I live in the US and I did follow the process to stop receiving the junk mails via ftc.gov.
Displays appears to be a reputable journal run by a reputable publisher. (Elsevier may be problematic in many ways but they still fit that category, in my opinion.) So I would not call this "spam". I would assume this is a good-faith review invitation from an editor who is simply mistaken about your suitability as a reviewer. Perhaps they are confused about your field of study, or have mixed you up with another researcher with a similar name.
I would simply write back and decline the invitation, explaining that it is outside your area of expertise. You could add that you are not interested in reviewing for this journal in the future. You could also ask them how they came up with your name as a potential reviewer; maybe there is a source of misinformation somewhere that you could correct. If you don't find the response acceptable, you can escalate and contact the editor-in-chief or the publisher.
The registration emails are an artifact of many editorial management systems which require a potential reviewer to be registered in the system before they are invited. I agree they are annoying but I don't think there's much to be done about them. Just ignore and delete if you are declining the invitation.
You could attempt to filter such emails with general spam filtering tools (which are outside the scope of this site). It would not be hard to filter future emails from this particular journal. However, it may be hard to filter review invitations more broadly without also filtering out ones that actually interest you.
The information at the FTC site does not appear to be relevant to journal review invitations. In fact, the US anti-spam laws apply only to messages whose primary purposes is the commercial advertisement or promotion of a commercial product or service, which in my opinion would not cover a review invitation. Anyway, in general, reporting spam to government agencies such as the FTC is almost always ineffective, and in this case I think it's actually inappropriate, since the evidence suggests that the email was sent in good faith. In the (admittedly unlikely) event that the FTC decides to do anything about it, it could cause problems for the journal.
