I don't think America has had a President that even compares to Cain. Really our wars, even the worst acts are done to limit as much life that is lost and end the war as quickly as possible. Even the dropping of the atomic bombs on Japan was done to prevent an even greater loss of life. If they hadn't worked, there would have been a ground invasion of Japan. We're still losing the Purple Heart medals that were made for the estimated number of soldiers who would have been harmed in battle. Not to mention the total number dead on both sides if it had happened. It was a terrible act, but it prevented an even worse act.
What Cain did was kill some people who did nothing wrong in order to continue a mission of revenge. She had no hope of surviving and even if she did, where would she go? The Colonies are nuked out wastelands with almost no survivors other than a few resistance fighters who would likely die from radiation exposure as soon as they ran out of medication. They could never take back the Colonies and survive there.