You are right in that copyright laws, and the status of individual works, can vary from country to country, although the EC has recently implemented a common system, which meant that some works which were out of copyright in the UK under the 50 year rule came back into copyright when the EC introduced 70 (or was it 75) years.

I think that anything published before 1900 is out of copyright everywhere. I believe that there are special agreements between USA and some countries to honour their respective copyrights even if this conflicts with the local rules.

Altogether a minefield! The enforcement agencies in each country should have the details, but I wouldn't like to rely on them.