I think it's pretty significant that President Lee mentioned the 1997 financial crisis: arguably, it was Korea's version of 9/11. It shook the country in a way people didn't realize was possible, and the country was, in a sense, never the same after that.

Imagine a US politician saying "agreeing to this would be a disaster at the same level as 9/11."

Lee is basically telling Koreans that this is something he can never let go through, and he'll do everything to stop it from happening. (Of course whether Koreans buy it is another matter, but after watching ICE arresting hundreds of workers, I think most are willing to believe Lee rather than the US government.)

I heard that he was considering going to the recent Beijing meeting where Putin was, however he heard that Kim Jong Un would also be there, so he decided against it.