That said, I can't see the advantage to any one player in taking out Washington DC unless they can shift attribution to someone else. I mean the small crazies (DPRK etc.) might want to do so but have to know that even success would be fatal to them. And the big crazies (Putin, the Ayatollahs, whoever's really running the show in China) would be too concerned about the consequences.

Not saying it couldn't happen, but the odds are, any entity capable of carrying out such an attack successfully has enough to lose that they would be dissuaded from doing something that would have extremely unpredictable consequences.