At the very least, the self-inflicted damage by Trump reflects a missed opportunity, because he could not have asked for a better partner than Moon to help handle the North Korea crisis. South Korea’s previous presidents, Lee Myung Bak and Park Geun Hye, talked a big game about pressuring North Korea, but they always wilted when the Kim regime stepped up its brinksmanship. In contrast, Moon has been in lock step with Trump’s push for maximal pressure and sanctions, and has demonstrated that he would deploy merciless force should Kim initiate a war. By gratuitously insulting and engaging in a trade war with the ally most willing to work with him, Trump risks a separation between the United States and South Korea.

This would be a terrible outcome, not in the least because it is exactly what Kim Jong Un wants. Washington distancing itself from Seoul may well embolden North Korea to spark a second Korean War that would kill tens of millions. To prevent such an outcome, South Korea may develop its own nuclear weapons as it once tried to do in the 1970s. This will almost certainly prompt Japan to develop its own nuclear weapons, which in turn would likely prompt China to augment its nuclear arsenal. The whole of East Asia, home to 1.6 billion people and the world’s most-significant economic region, would turn into a nuclear tinder box.

Ironically, the only reason why a U.S.-South Korea separation has not yet happened is that South Koreans do not take Trump seriously. In early August, when he promised “fire and fury” against North Korea, South Korea responded with a yawn. The local media duly covered Trump’s provocation, but also included the follow-up statements from McMaster and Mattis—with a wink and a nudge that the former generals, and not Trump, were really in charge of the U.S. policy.

With Trump’s latest threats to withdraw from the KORUS FTA and his criticisms of the supposed South Korean appeasement, the reaction in South Korea has been the same: indifference, with the expectation that the grownups in the White House will step in. “Opinion polls show South Koreans have one of the lowest rates of regard for Trump in the world and they don’t consider him to be a reasonable person. In fact, they worry he’s kind of nuts, but they still want the alliance,” David Straub, a former State Department official who recently published a book about anti-Americanism in South Korea, observed.

In one sense, this is a hopeful sign. U.S.-South Korea relations may yet survive a U.S. president who is disrespectful of the alliance. But that is not to say the damage has not already been done.