(Spoilers) What if Travis
had killed Palantine? What would have happened afterwards?
shareArrested or shot by Secret Service? I don't think he would have walked away from that one. He might have managed to kill or wound one or two other people, but I think it would have been the last of Bickle.
If you mean larger ramifications, it would have been the same thing that happens in the wake of any assassination or attempted assassination: news cycles, grieving, people taking advantage of the power vacuum, sentiment and cynicism.
This would have likely shaken up Betsy, psychologically-speaking, quite a bit.