I am not surprised that the U.S. government would not side with anyone over this dispute. I would think the U.S. government may look at this as why should it put its relationship with Japan at risk because the Moon administration over reached in its Japan bashing for domestic political reasons and is now paying the consequences.:
The United States takes the tensions between Korea and Japan very seriously but cannot play a “mediating role,” according to the chair of the Korean National Assembly’s Foreign Affairs Committee who said the message was relayed to him by the U.S. State Department point man for East Asian affairs.
Rep. Yoon Sang-hyun, a third-term lawmaker of the main opposition Liberty Korea Party, met with David R. Stilwell, the new U.S. assistant secretary of state for East Asian and Pacific affairs, Wednesday evening amid the diplomatic spat over Japan’s recent export restrictions on Korea.
Yoon told the JoongAng Ilbo over the phone that Stilwell told him that the United States “could not take one side or the other because taking one side means losing the other.”
Stilwell then conveyed, according to Yoon, that Washington “encouraged its two friends,” Seoul and Tokyo, “to resolve the issue through dialogue.”
Joong Ang Ilbo
You can read more at the link.