As an artist, you should register your works with the USCO so you can assert your rights against any violations.
While registration with the US Copyright Office (or USCO) is recommended, it is not required to obtain copyright protection in your work. Under US copyright law, the moment your work is fixed in a tangible form, it is protected by copyright law.
If someone does infringe your copyright, it is necessary to register your work before bringing a lawsuit. Registering your copyright before the infringement allows you to recover certain kinds of damages. Best practice is to always register any significant work before distributing it to the public.
For more information on how to register your work with the USCO you can visit their website at: https://www.copyright.gov/registration.