If you're worried about infringement, register your work with the US copyright office. You can only get monetary and statutory damages if the work was registered before infringement, otherwise you can only get an injunction. But you can't even file a claim in court to request an injunction without first registering the work. Basically, while copyright nominally attaches at creation, without a certificate you can't press any rights in court.

You don't need to register each release, so long as a material portion of the registered work exists in subsequent derivative works.

Without a registration threats of a copyright dispute are mostly noise to someone savvy enough to know how the game is played. If they think you'll persist they can just replace the infringing work or cease distribution, which is a hassle but not a significant deterrence for bad faith actors.