Can a rear end collision damage the rear oxygen sensors and the fuel system?

yes it can, depending on year of vehicle. MID 90'S ON UP HAVE FUEL SHUT OFF RELAYS. upon impact they are designed to (trip) and avoid possible leaks, or ignition of fire upon impact. if vehicle will not start after impact check owners manual for location of fuel cut off switch and reset. MAKE SURE YOU CHECK LINES,( fuel system ) for leaks IMMEDIATELY.