@Bruce Coulson: I think that the governments of the world would treat the various supernatural nations the way they do extremely powerful organized crime groups. At a certain point, the politicians get scared and let the mob operate as long as it isn't too blatant.
Look at the way Marcone operates in the books. He's making and enforcing his own laws, and he gets away with it because he's powerful and well-connected. Actually, the White Council is very similar to Marcone's mob in that it keeps the really nasty types down by enforcing its own laws. And in that everyone in their field is terrified of them.
And the FBI is after Marcone, he's just hard to nail. If Marcone was not a citizen and didn't live in the U.S. then some of the kids' gloves would come off. We (the US) get intel on terrorist camps and we just bomb them. Heck, we've even done that to other countries easily enough. If a supernatural groups started messing around, we'd get the capability to stop it and then we'd implement it. Maybe we'd play along until that happened, but once it did we'd make it clear they had to back the hell off.
Here's what happens if the Supernatural Community becomes known in the US in the Dresdenverse. The government will offer to employ good, american wizards and others to help them figure out how to handle the Supernatural, and they'd probably pay top dollar given the limited number of people. I think most American Wizards would find that pretty appealing. They'd get scientists to start studying the nevernever, hexing, and other things and figure out how they'd work. I think a few thousand scientists working hard at the problem would find at more than a few hundred wizards who tend to keep a lot of secrets from each other. Technologies would be developed to detect and deal with supernatural entities. Ones that could be dealt with reasonably, like the Fae (who honor contracts), most wizards, many old gods, the Knights of the Cross, and so forth would be dealt with fairly (there might be some problems here at first). Ones that harmed American Citizens and that was inherently part of their nature would be first detained, probably some study, and eventually they'd probably just be killed or jailed wherever they were found. Likely for some of them, like WCV, researching cures would be looked for. Others, like Red Courts, would probably just be killed as they are demons that have killed American citizens. People like Dresden or Michael would get entire tactical teams under them to help track down and eliminate threats.
If the White Council fought that sort of thing, fought people defending themselves, then they'd fall apart...the only way they could survive, which is their top priority, would be to cooperate with governments. They might not be calling all the shots anymore, but they could probably work it so that they had a good bit of clout, AND potential wizards and other talents could be found by a lot more people and sent to them for guidance and training.
Would there be problems? Would there be cities destroyed? Innocents killed by governments? Sure, but overall it would be a positive thing for humanity and mortal practitioners. It would be a negative for the White Council (less power, even if they have more wizards in the world), and a negative thing for other supernatural organizations and groups. That and perhaps fear of the initial (first couple of decades or so) death toll are the likely reasons they haven't revealed themselves -- well, and fear the inquisition, but seriously, that's NOT going to happen in a modern world with things like Harry Potter and so forth so popular. You'd have a few nuts, but no government movements there...especially when magic would be so useful.
Well, of course the real reason this isn't done in the books and hasn't been done is that the conceit of the story is that it is just like our real world with the supernatural hiding. You have things out in the open and that's not the case anymore, and so the story loses that part of its charm. Of course, humans would behave more believably (we're curious creatures, not people that collectively put on blinders to stuff happening all over the place), so there'd be a positive to that. In a sense, Harry Potter is the more believable universe since they can magic people to not believe things..whereas that's not allowed in the Dresdenverse -- in the DV this is done so we can have people like Murphy and Marcone though, so it's not all bad from a story perspective.
