I recently rear-ended another car at about 15mph in my 1992 Saturn SL2.
There is some minor damage that I repaired easily: broken plastic on the horn, non-functioning light, cracks in plastic bumper, broken plastic fasteners.
The more substantial damage is a bent radiator (not leaking) and a bent internal metal bumper. The metal bumper behind the plastic and foam was bent enough that it is cracked halfway through.
Other than providing protection for collisions, it doesn't seem to be a structural part of the chassis. Is it? What are the consequences of leaving this unrepaired, or a simple repair, like a steel plate over the cracked portion?