International Copyright Law
Everything you've learned so far applies to U.S. copyright law. Things may be different in other places. Most of the European nations and many other countries around the world have agreed to follow the basic copyright laws of the Berne Convention. There are also other treaties and conventions covering copyright and intellectual property rights that some countries follow, but a number of things in each are left to the discretion of member countries.
Many countries that are not part of the Berne Convention have radically different copyright laws. Some have no laws protecting you and your songs. Every country is different. You could probably study for the rest of your life and not know half of the copyright laws in the different countries of the world.
It's very important to know that you'll need a different publisher, called “a sub-publisher” or “sub-pub,” in each country where your copyright is recognized and your song is making money. Sub-pubs represent your copyright interests in their respective countries and collect your nonperformance-based royalties for a percentage of the song's earnings in that country. The idea here is that the sub-pubs know the laws in their country and, since sub-pubs work on a percentage, will do their absolute best to collect all monies due and help your song achieve its maximum earnings potential.