Narratives of crisis in the U.S.-South Korea alliance, however, are misplaced. After conducting research on the role of norms and alliance management, my co-author and I argue that alliances among democratic partners tend to demonstrate greater resilience and flexibility relative to alliances that lack any norms of democratic consensus. In particular, policymakers in Seoul and Washington share a strong consensus on the value of the security alliance.
It’s true that there has been a consensus about the value of the alliance in the past, but this may underestimate the strains that Trump has already put on the alliance with his erratic and confusing positioning in just the last few months. He has simultaneously alarmed  South Koreans that he might trigger a major war and worried them that he might try to make a deal that would affect them without consulting them. His ignorant claim  that Korea used to be part of China outraged the South Korean public in another needless provocation.
More recently, Trump has declared  that South Korea will have to pay for the THAAD missile defense deployment (contrary to an existing agreement), and then McMaster reassured  them that it isn’t so. Adding to the confusion, there are reports that Trump became furious  with McMaster for contradicting his random statement, which creates the impression that McMaster’s attempt at reassuring Seoul doesn’t reflect the administration’s real position.
Trump’s first statement prompted Moon’s camp to question  whether their government should have allowed the deployment in the first place. The new government is now likely to review the entire policy and may end up scrapping it all together. Given that the deployment has already prompted Chinese economic  boycotts  of travel to South Korea and South Korean firms, South Korea is already “paying” for THAAD with lost business and increased tensions with Beijing. There is understandable wariness about proceeding with the missile defense system as a result, and Trump’s clumsy interventions have only given South Korea’s government more reasons to reconsider the arrangement. Persuading the new South Korean leadership that the deployment is worth those costs would be a challenge at the best of times, but it is bound to be more difficult when our allies don’t know which statements from our government to believe and which to dismiss as more of the president’s gas-baggery.
In order to manage an alliance successfully, there has to be some basic understanding of the allied country’s interests and concerns, and Washington has to treat the ally with some respect. To date, the Trump administration seems to lack the former and has failed to show the latter. The alliance will presumably survive, but unless the administration coordinates and consults with Seoul much more than it has the alliance will deteriorate steadily over the next few years.