The reason I am looking into if I can register the images with the USA Copyright Office is that I have reason to worry that a USA agency and their client may infringe the copyright of my images in numerous countries. By registering the images, which I have found I can, prior to the infringement allows me to take action in the USA where statutory damages and 100% legal fees are awarded for a blatant infringement by experienced parties such as multinational
agencies & worldwide clients.
Statutory damages and 100% legal fees are only available if the image is registered prior publication or if previously published the registered prior to any future infringement. Without a registered copyright most lawyers will not take the case on unless you personally have deep pockets to cover the legal fees.
One cannot really stop them from stealing but you can get well prepared to deal with then if required.