What he was doing wasn't necessarily a bad thing. He could have spent the post-war period fighting for the American ideals of justice, equality, and tolerance that, in his timeline, American didn't start living up to until well after the 20th century. Or at least, he'd have tried to until someone said, "hey, why should we let someone from the future tell us what to do. How do we know he really is an American," and he just said "Screw it. I don't need this. I'm going home. I never liked having to wear pants anyway."