There isn't one Public Domain
On January 1, 2020, copyrighted works in the US started to enter the public domain. The public domain refers to materials that are no longer protected by intellectual property laws such as copyright. These works are now owned by the public and anyone can use a public domain work without obtaining permission.
Works haven't entered the US public domain for the last 20 years because the Copyright Term Extension Act (CTEA) of 1998 had extended copyright protection to the life of the author plus 70 years; and for works of anonymous, pseudonymous or works made for hire to 120 years after creation or 95 years after publication, whichever ends earlier (17 USC 302).
Copyright protection outside of the US however generally is based on the life of the author plus some years (typically 70 years) (see Wikipedia chart).
China = Life + 50 years
Germany = Life + 70 years
India = Life + 60 years
Thus, a copyrighted work could be in the public domain in the US and not outside of the US, and vice versa. Therefore, if you are using a public domain work, you should confirm that the work is actually in the public domain in the relevant countries.
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