I think that the main thing that protects most of us here in North America from bike theft is the perception among most criminally-minded people that bicycles just aren't worth stealing. As bicycles become more common here, that will change.

In the meantime, if a thief really wants your bike, it's gone. No lock will protect your bike from an organized, somewhat intelligent person with battery-operated power tools. Fortunately, most thieves are not so well prepared. Bike theft is more often than not a crime of opportunity. I personally think that bike theft is a big problem in Europe in part because many people there use absolutely ridiculous locks. If you use a really good, short U-lock, lock it up in well-traveled areas, don't leave the bike out over night, and avoid college campuses like the plague, your bike is a lot less likely to be stolen. In my entire life, I've had three bikes stolen. One was stolen in Bremen, Germany, and it had one of those stupid frame locks that prevent the wheel from turning, but it wasn't actually locked to anything. The other two bikes were stolen from front porches, and were not locked up at all. I have never had a bike stolen that was locked using a decent U-lock, nor have I known anyone who has. I'm sure it happens, but a good lock and some common sense will vastly improve your odds.