Why hasn't the Trump administration nominated an ambassador to South Korea?

Why hasn't the Trump administration nominated an ambassador to South Korea?

A large number of State Department positions remain unfilled as President Trump and Secretary of State Rex Tillerson continue to send mixed messages on North Korea. The U.S. ambassador to South Korea could help clarify things - but the Trump administration has yet to nominate and confirm someone to the position. "It's a huge deal. First of all, when you think about the stakes in play over in North Korea, we absolutely need someone there who is representing us interest," Harry Kazianis, Director of Defense Studies at the Center for the National Interest, said to the Washington Examiner. Below, we look at why the position remains vacant:

Why the vacancies are concerning:

Career State and Defense officials can cover the vacancies, but even a brief vacancy can impact long-term decision making:
"Career officials who are filling in have a lot of difficulty reaching final decisions on policy recommendations — because they are, by definition, only in charge of that decision temporarily. Getting people into top positions is necessary to start giving the policy process a sense of permanence and direction," wrote Zack Beauchamp at Vox.
The vacancy goes beyond the U.S. ambassadorship to South Korea, too: There is no assistant secretary to the East Asian and Pacific affairs in the State Department, and no assistant secretary for Asian and Pacific security affairs at the Defense Department.

The Chargé d'Affaires is filling in - but they're no substitute:

If South Korean President Moon Jae-In called the U.S. Embassy, Marc Knapper, the current Chargé d'Affaires, would answer. Knapper began his term as Chargé d'Affaires at the U.S. Embassy in Seoul on January 20th, and previously served as Deputy Chief of Mission in Seoul.
The position doesn't require Senate confirmation, but few believe that Knapper is a long-term substitute. Knapper simply does not have the close relationship to the White House expected of an hand-picked ambassador.

The failure to nominate an ambassador is on President Trump, not the Senate:

The State Department has faced repeated questions regarding its unfilled positions, and the White House has opposed a few of its appointments.
"I decided that maybe if I start naming people to office when they're eight or nine years old, they'll be of age by the time we can get them through the process," Tillerson said, referencing the slow pace of confirmations from the White House.
In late June, a South Korean newspaper reported that the White House had tapped Victor Cha, a professor at Georgetown, as the next U.S. ambassador to South Korea. But that nomination has never been made official.