I actually know a fair amount about our BMD systems, and I can tell you that they are universally useless. The main problem with ours currently is the phase for which they are designed, but in the end you will see it doesn't matter so much. There are 3 phases in a ICBM's life, the boost phase, the midcourse, and the terminal phase. We attempt to intercept in the midcourse phase.
The problem with midcourse interception is that it is insanely vulnerable to countermeasures. Since it is trying to intercept the missile in space, decoys are incredibly effective due to the fact that a deployed decoy balloon and a deployed warhead behave in very similar ways due to the lack of atmosphere/gravity working upon them. The cost to implement these countermeasures on missiles is VASTLY lower then it is for us to come up with new systems to detect and ignore those countermeasures. In effect, we will have to spend a hundred times (or a thousand times) what other nations do just to try and stay ahead of their relatively simple to implement countermeasures. Decoy balloons are just one of dozens. In effect, it's a money and R+D race that we are now losing before we even got our missile system started. Mid course intercept is crap... and our whole system is based upon it. Sucks, huh?
If that's the case, we should look to other phases right? These suck too unfortunately. As for the boost phase, the main problem is proximity. If you're going to intercept a missile on the way up your interceptor needs to launch from a place close to it, or you'll never catch up to the missile in time. This requires deployment of interceptors in dozens of different countries around the world which implies severe diplomatic problems, and it still wouldn't work for ICBM silos in the middle of China or Russia. An alternative to that is this old program you might have heard about called "Brilliant Pebbles", which is a collection of space based boost-phase interceptors. Sounds like putting them in space would work wonders, right? Wrong. No more proximity problems, but not only are they hideously expensive, space based weapons are extremely vulnerable to attack. (they are locked into predetermined orbits, they can't hide, and they are sort of delicate by nature. Witness the development of ASAT weapons.) So that's a bad idea too. In here is where the air based lasers go, but they are A.) vulnerable to attack and B.) require a constant patrol by dozens (if not hundreds) of aircraft over all possible hot spots. Not effective either.
Lastly we have terminal phase. This one REALLY sucks. In effect we would have to deploy interceptor missiles over every inch of the US, which would cost so much money and maintainence we would almost be better off letting them nuke a few cities... it would probably save money. In reality, there is no way we could ever cover all of our important sites with them... and so they would just launch somewhere we didn't have it. That, and even if you do hit the missile on the way down you are now raining radioactive debris all over your cities. Certainly better then it going off, but not a very ideal solution.
All that doesn't even mention how unlikely it is that any of these "rogue states" would be stupid enough to associate a heat bloom from an ICBM with a nuclear attack on us, when a truck or container bomb would serve the same purpose but without a guarantee of national obliteration.
What does it all mean? It means missile defense sucks, period. It has always sucked, and it shows no signs of not sucking any time in the near future. Our money is poory spent on this endevour. If we just absolutely HAVE to spend money on it we should be spending it on boost phase, as it might someday be effective. I would say cut funding entirely however.