The big difference is that the leader of the KKK is as far as I know not an official part of the U.S. authorities, and this general was... Now this would still be a violation of the sovereignty of the U.S. if Germany did such a thing (although I wonder what Germany has to win with that), but still...
Trump saying he doesn't want war with Iran sounds as credible to me now as a butcher who claims to be a very passionate vegan.