Secretaries Rex Tillerson and James Mattis recently wrote that the U.S. is not seeking regime change in North Korea. Depending on whether they meant it or not, this policy has enormous implications for the success of their putative policy, which is to remove the North Korean nuclear threat.
Their statement is clearly designed to calm down the North Korean communist regime. It is certain, however, that the regime will not calm down. This is because it is an illegitimate regime whose principal fear is of its own people. As George Kennan said of the USSR, it fears us not for what we do but for who we are - a democracy with a competitive and threatening legitimizing concept of state authority: the consent of the governed. Nothing the U.S. does, short of renouncing our political system, will diminish North Korean, or for the same reason, Chinese, fears of the U.S.