worlds keeper?

North Korea is developing nuclear capabilities and we (US) are nervous.  We don't think they should have Nuclear capabilities, especially, long range capabilities. Seems that we are afraid that they might use that as a threat to other countries in an attempt to influence those countries toward North Korea's interests.  Places like those in the Middle East.  Places like we have already done similar things!?

The Soviets and us wrote the book on muscle flexing.  Together we have enough nuclear warheads to virtually make mankind extinct.  I guess the difference is that we are smart enough to only use our might as a threat?  All the might that we possess has not been much of a deterrant to other countries of late.  We constantly engage in skirmishes in remote parts of the world only to expend considerable money, material, and lives with no clear victory.  It would seem that after WWII we have become soft.  We have had a string of embarrassing "wars" with no clear victory.  Korea, Viet Nam, and a dozen other military debacles.  While we exhibit the ability, we do not exhibit the desire for quick, decisive results.

Could it be that with North Korea and others, we fear that they might have the courage to back up any bravado?  What makes us so certain that we are the only country capable of proper use of end of the world power?  I am not advocating Korea's nuclear power is a good thing,  rather I question our ability to really be the worlds keeper.