@Tyler bro my take, they want to put a leash on this 2 East Asian country. There is a brotherly love between China and SK, SK is comfortable living under Chinese hegemony since ancient time and assimilation could have happen if Japan hadn't invaded it. And without the US both JP and SK will be at war. With that as a context the US want to channel the two animosity toward China.... HAHAHA, will that work? if you believe their words and suggestion then I have a bridge to sell you...LOL
You have no grip on the reality of South Korea. There is no such thing as a brotherly love between China and SK, period. South Koreans are more anti-China and China-resistant than Australians/Americans/Indians ever are in terms of the general populace and media.
S. Korea is an extremely (pretty much the most) homogenous, closed and insulated society and they live in their own version of the world and it is incompatible with the outside world. They don't get along with any of its neighbors. S. Korea can't coexist with N. Korea, can't coexist with Japan, can't coexist with China, can't coexist with SE Asia. Period.
Since ancient time? SK is no Choson or Koryo. It's an artificial and undeserved creation of post world war 2 by the US as part of neutralization of defeated Japan.
When did Japan invaded it? Did Japan invade it continuously throughout the history? No. China had plenty of time but why assimilation never happend in the long history? The Japanese mistakenly thought that they could assimilated them by treating them as the same people and they are paying the price. Don't repeat the same mistake.
It is very strange that S. Korea always gets spared by neighboring powers and maintains mistakenly favorable image.
I think there are two reasons for that:
1. S. Korea is a small minor country in the middle of great powers. So S. Korea is always viewed less of a threat in front of bigger powers and the powers want to have S. Korea in the middle on their side to counter their bigger, more serious enemies.
Japan has supported S. Korea to counter China, N. Korea and the Soviet.
The US supports S. Korea to counter Japan, North Korea, and China.
China supports S. Korea to counter Japan and the US.
The rest of the world is nervous about China's growing power so supports smaller, less dangerous S. Korea as an alternative, while China supports S. Korea because S. Korea looks less attached to the US than Japan is to the US.
S. Korea gets favorable treatment by all parties because of their position, not because they deserve it.
2. S. Korea is such a minor, less important country so always gets little attention. Few foreigners are interested in and seriously study about S. Korea (aside from sugarcoated k-pop and k-drama fans etc). Few foreign journalists live in S. Korea to report coverage, and Korean is a minor language only spoken by Koreans (in contrast to major languages like English, Chinese, Japanese and Chinese-speaking Taiwanese and English-speaking Indians) and language barrier is very high and very few people understand the Korean language and know what's said among Koreans. That's why I say S. Korea is very insulated from outsiders. The raw reality of S. Korea less likely gets out and catches little attention outside. People outside only see the sugarcoated k-pop images that S. Koreans want to show to others.