[emeritus]

Copyright law in the US was long different from the rest of the world in that you had to file a copy of the work with the library of Congress to get copyright protection. Elsewhere, copyright came into existence automatically . The US only fell into line with the rest of the world in the late 1990's. I forget what the transitional arrangements were, if any, but for older stuff, no registration= no copyright in the USA, hence public domain in the USA. Copyright would still exist in other countries. Copyright law is fiendishly complex and the goalposts get changed periodically, often by international agreements that always seem to extend protection. Paying to renew copyright, once only, is a peculiarly US thing. Elsewhere it comes into existence and remains in force until it expires.