Being an unreasonable, unmeetable deal on paper is just a feature. You're not supposed to meet the text of the deal. You're supposed to get under the table and ask "how can we facilitate this?" while palming a hundred dollar bill. It's like a police shakedown in less stable countries.
A more serious question for Korea is the US military protection against North Korea and/or China. They may yet end up in the unthinkable alliance with their historic enemy, Japan.