It is true that copyright registration is required before a copyright owner can file a copyright infringement action in US Federal Court.
It is also true that if you havent registered your copyright with the US Copyright office in advance of an infringement, then you wont be eligible to seek statutory damages in US Federal Court, and will only be able to seek actual damages after registering your copyright(s).
Your copyright does not have to be registered with the U.S. Copyright Office for you to take advantage of the Digital Millennium Copyright Act (DMCA) provisions in US Copyright law. DMCA is a means to seek monetary compensation for an infringement. The DMCA allows for damage awards from $2,500 to $25,000 plus attorneys' fees and court costs.
By comparison the statutory award for an infringement has a maximum limit of $150,000 per willfully infringed image, making timely copyright registration well worth the effort compared to using the DMCA.