Easy choice. America, as its quite possibly one of the greatest mistakes in all of existence.
To be particular, your chain of command started the horrors of nuclear fallout by condemning Hiroshima and its harmless citizens to either instant death and radiation poisoning all those years ago. Your public is divided between political affiliations, race, lifestyle and key interests. While they are also as innocent as to believe your nation is one of 'the good guys,' the goodness can only be measured by the virtues of all its citizens and how they work together. That's up to you guys.
You have also proceeded to bomb many countries in order to either halt their development or limit the amount of control they have over their own resources. List is here: http://www.btinternet.com/~davidbeaumont/msf/listbombed.html
If I had to place an explosion tactically, it'd detonate it right smack in the centre of the Pentagon, while your president is in for a visit- I'm sure your chain of command has to go or change anyway. Like I said, I don't have a problem with your public and I'm sure that given the proper incentive to take control over their lives without the fear of debt or authority hanging over their lives, they'll prosper without their leaders or the inflictions of administration. That is, of course, if they don't riot in the streets in a fit of savagery, like what happened in Croydon.
One thing that I wouldn't do is set off the many nuclear armaments you already have. Sure, I'd have to go in and take them myself after the damage is done and dismantle them, to make sure nobody from your new administration rages like a little girl and takes it out on other parts of the world.
I hope that answers your question. Don't hold it against me, that government's just responsible for many evils, and it should end with them. At least the chaos that ensues cuts the line clear for the rest of that society, defining what is inherently good and what is inherently evil with all of its individuals, and deciding what side they stand on. Then, the other countries of the world will send over spy planes and judge for themselves what the real calibre of your post-apocalyptic society is.