Advertisements promoting the antibacterial effects of various products give the impression that wiping a surface with the disinfectant will kill household germs immediately, leaving a sterile surface. Can this be true? Surely, the bacteria must take a defined time to die? Thank you.

Well yes it would take a finite amount of time, but depending on quite how the cleaner works it could be effectively instantaneous (i.e. a tiny fraction of a second). Something like neat bleach is incredibly toxic, so at the scale of a bacterium you are pretty much drowing them in neat poision. And since they are only single cells, it's not going to take long for them to die (a human say would still survive a few seconds as it would take time for the stuff to penentrate the skin and kill off major organs etc.) as it only has to penentrate the cell membrane and then break that or kill a few major organelles etc. and the cell would be dead or unrecoverably damaged.