8-Ball is a very popular game worldwide. However, as you noted in your question, there are competing sets of rules. Unlike other sports, there is no single authority for pool that sets the rules for this game.
The World Pool-Billiard Association (WPA) is probably the most geographically widespread of the tournament organizations. The Association is made up of 6 regional confederations around the world. (The Billiard Congress of America (BCA) is one of these 6 confederations.) The WPA is a member of the World Confederation of Billiard Sports, which is representing cue sports to the International Olympic Committee in an attempt at inclusion in the Olympics.
The WPA publishes World Rules of Play for various games, including 8-Ball.
The American Poolplayers Association (APA) claims to be the world's largest pool league, in terms of number of members. In addition to the United States, they have affiliates in Canada and Japan. They publish an 8-Ball & 9-Ball Game Rules Booklet (pdf), which is available for free online.
The Valley National 8-Ball League Association (VNEA) is another large, international league with their own rules for 8-Ball.
In addition to these, lots of individual venues have their own rules of play, used for informal games.
Each of these organizations has international tournaments, and professionals will play by the rules of whichever tournament they are participating in. However, if you are looking for one, canonical set of rules for 8-Ball that is recognized by everyone worldwide, that does not exist.