First of all, thank you for answering my question in properly!
You know I agree that these countries might be a threat to some of their neighbors, but I think US interference could even make the situation worse. Us Should let them solve their problems by their own or by the help of UN.( I still don't know why US politicians thinks that they have the right to interfere in everything which's going on in the world!)
Right now US isn't going (and probably can't do anything) to do anything about Pakistan and India since they have nukes. and I'm sure 2 countries with nukes aren't crazy enough to start a war against each other and they have to put up with each other anyway.
As for N. Korea, I'm hopeful that N. and S Korea solve the problems between themselves and after that I think there would be no need to worry about N. korea as well.(perhaps I sound very naive or optimist here! But I think UN should work on it)
Right now the only problem is with Iran. As SOS2008 mentioned Iran and US could solve their problems.
You say Iran is a threat based on their hostility to the US and the possibility of their interfering in Iraq, but honestly what's the reason of this hostility ? I'm sure you know the reason better than me, but anyway do you think attacking Iran could make it any better? And What makes Iran to interfere in Iraq? Don't tell me it's only because of cultural similarities. If you ask me it's only because of the threat of US to Iran. Anyway I think there are other reasons for attacking Iran and these are only excuses. Sounds like US want to have all control and power over ME!