If there is to be a second coming, IMHO, Christ will be alone. Man will have destroyed himself well before then. I dont see it as bombs, I see it more as biological warfare. I dont see this happening in our lifetime.
I too see the US as an early ancient Rome. We do have the advantage of communication that the Romans lacked. I cant see the country falling apart like Rome did, but I believe that there will be major changes in the government before we are dead. Not necessarily like a second civil war, it will be political and commercial. Then we can all sit in our perfect rooms, have sex with these weird headpieces, get fined for saying [censored], eat at Taco Bell and drive 442s.