When your disapproval rivals the time when you killed school girls with your military vehicle:

The unfavorable opinion on the U.S. among Koreans reaches 2002 Yangju Highway incident aftermath level in 2026. 2003 was the peak anti-American year for Korea as the U.S. troops killed two school girls with a military vehicle in a training accident and the U.S. government didn’t punish the soldiers who did that.

Source: https://www.pewresearch.org/short-reads/2026/08/24/how-south-koreans-view-their-relationship-with-the-us/