What of we replaced Schr�dinger's cat with a bomb?

No. You would need a bomb in a box in a box. The cat cannot be observed/seen until the box is opened. In your scheme, the bomb in the box IS equivalent to the cat, as the result of the atomic decay will be seen immediately it happens. It cannot exist in a superposition of states, as the superposition of states exists only when not being observed. With a bomb in a box in a box this situation can occur, as we cannot know whether the bomb has exploded.(destroying the first box), until we open the second box!