Each country has its own rules for what works are protected, and when a copyright infringement suit may be brought in that country. A suit may be brought in any country whose laws permit it. If the defendant has no assets in that country, collection of a judgement, if one is awarded, may be harder, than it would nbe in the defendant's country of residence.
In general, suit may be brought in any country where an act of infringement takes place, if the work is protected under that country's copyright laws. However, some countries do not allow suits to be brought against non-resident defendants.
If the copyright expires on different dates in different countries, posting it on the intenet may well be infringement in any country where the rights have not expired, and suit may well be possible in any such country.
Some countries follow the 'rule of the shorter term" and end protection whenever the source country does. The US, for one, does not follow that rule. US copyright of a foreign work lats as long as it would if the same work had been created and published in the US.
Unless the work is PD in all of C1, C2, C3, and C4, it may be possible for the copyright owner to bring and win an infringement suit. Indeed it may be possible for a suit to be brought and won in C5, a country where the work was downloaded and further copies made, even though neither the host, the servers, nor the poster are located in C5.
Not also that the work's "country of origin" may include the country where it was first published, or the current residence of the author, as well as the author's birth country or country of citizenship. Thw works "country of origin" often matters in copyright cases.
Under the Berne Copyright Convention, a non-resident or non-0citizen must be granted at least the same rights to sue for infringement as a resident or citizen, and could be granted more rights in any country that adheres to the Berne convention. Countries that adhere to the WTO's TRIPS agreement must also treat foreigners at least as well as their own nationals. The UCC is effectively obsolete, but would have imposed similar requirements.