〝一枚岩〟となった日米韓の離間を狙う中国

China aims to separate Japan, the U.S., and South Korea, which have become a “monolith”.

引用元(reference)：https://www.sankei.com/article/20240526-ODTKC2YMEBJCXKQY3RTFW65BW4/

意味：1枚の板のように平らで大きな岩。また、そのように、組織などがしっかりとまとまっていることのたとえ

Meaning:　A large rock as flat as a board. Also, a metaphor for the firmness of its organization, etc., as such.