The nuclear weapon was created to destroy and kill on a massive scale. As president, it was Harry Truman's decision if the weapon would be used with the goal to end the war.
Well he is basically letting serial killers go off onto the streets and into everyday peoples lives. They will involve themselves with people and eventually kill or cause harm to people again. They wont learn from there mistakes if they dont get punished for them.
Americans believed Europeans forced the United States into imperialism. Americans enjoyed the greater territory and power imperialism gave them. Americans thought it was unimportant to expand outside of North America.