If you hit the car entering the roadway - their fault
if you hit a car in incoming traffic - your fault
hit a pedestrian - your fault
think of it this way. Car pulls out, you swerve and hit something, original car drives away. "Officer I missed a car that pulled out and it drove away"
I've heard that with video evidence you can try to prove that the other person was the cause of the accident (without actually getting hit) and in those cases you can have the other driver charged and maybe get insurance to rule in your favor but the chances are slim and most people won't have video as dashcams aren't nearly as prevalent here as they are in places like Russia (hence why we get so many crazy Russian driving videos).
Even that was new to me as I always thought if you don't actually get hit you aren't considered involved in the accident but I've read a few stories lately of people getting charged for leaving the scene after they cause an accident but don't get hit and just leave.