It seems forgotten in the euphoria of the ending, but did the H-bomb do anything at all? Miles got the message from Juliette that "it worked" and we were led to believe that the bomb created the alternate timeline we were watching with the plane landing safely. The finale tells us that the alternate universe was not a result of the bomb at all and wasn't an alternate timeline anyway, just transition within the afterlife.
At the moment we thought the bomb exploded there was a simultaneous time shift that transported everyone 30 years later which is fine, but why wasn't Juliette also transported? She was still alive. Her broken but still breathing body should have been at the bottom of the pit where the hatch was. If you conclude she died because of the explosion, then everyone should have died. And since the alternate world wasn't created by the explosion, then there probably wasn't an explosion at all. That would be the only explanation because if the bomb went off there would have been a huge crater at that spot after they flashed forward because there really weren't 2 timelines after all, just 1 timeline with a lot of moving around.