Barbie realizes that the visitors on the other side are saying goodbye not hello to their relatives and friends on the inside, because the good old US military is planning on bombing the dome with the strongest non-nuclear bomb they can find, and Barbie is sure the bomb will not only destroy the dome but everyone locked inside it. Why is the military doing this? Not completely clear, but presumably because it's safer to destroy any threat we don't understand, rather than keep it around and risk it destroying us.
But the dome survives the bomb, and with it the relationships of the various couples who for one reason or another didn't take shelter below - in fact, these relationships improve as a result of their tempting and beating death, at least for now. First and foremost are Junior and Angie, who actually moves closer to Junior as the end apparently approaches for Chester's Mill. Norrie and Joe draw closer too, and even kiss. And Julia takes Barbie's hand. On this last relationship, it's beginning to look as if Julia's husband was a bad guy, killed by Barbie as some sort of military action. The husband certainly was no bargain for Julia, sending her some kind of Dear Joan letter as one of his final acts.
About the only relationship which doesn't improve as a result of this threat of extinction is Big Jim and the Rev's. Convinced that the Almighty not the mighty dome saved the town, Rev. Coggins makes the mistake baiting Jim one more time. Jim responds by killing him. Good. The character got on my nerves and killing him was the only logical move for Jim, given what the late Reverend knew about Jim's misdeeds.
So the dome was able to withstand an attack that reduced everything immediately outside it to rubble. An impressive accomplishment, which raises anew the questions of who put it around Chester's Mill and for what purpose?