B2s have been flying sorties out of Whiteman since 1993, and we had long rang bombing capability before that. Mid-air refueling is awesome.
Also, S.Koreans LOVE America. From the wiki on US-S.Korean relations.
And lastly, we have military aliances with S.Korea (and Japan), we
have to defend them. Part of defense is showing your enemy that they don't want to Eff with us.
i'm not defending the dprk and there's no doubt they're a militarist state, but it's worth examining why - they're scared of the americans doing what they did to iraq, libya and any other country that gets in their way.
That perfectly explains why the Norks never did any dicking around before 1991.
Except that they don't resent American presence, at least in the South.