Okay, let me chime in here. This year there are a minimum of FOURTEEN events with at least $25,000 in added money right here in the USA. Check it out: DCC, U.S. Bar Table, The Masters, FOUR Seminole Tour events, TWO Joss Tour Championships, the Players Championship, the U.S. Open Ten Ball, the U.S. Open 9-Ball, the World Straight Pool and the Ultimate Ten Ball in Dallas. Maybe I'm leaving something out here too.
In addition there are multiple regional events with 5K added or more, like the recent Seminole Tour event at California Billiards with 16K total in added money. So there are ample opportunities for a professional pool player to get in action every month in the USA. Plus, the U.S. is still a wonderful country to live in, with many beautiful (and inexpensive) places to live. Good deals on housing are available everywhere now. If you're European your money goes farther here than at home.
I can absolutely see why a pro pool player would chose to make his home here, if he (she) could. He (or she) can play on a regular basis here, and if they are good enough (like Shane for instance), they can also travel to the major international events. Makes sense to me.