The UN as Dr Alf says, is not adding proper value but is not in need of replacement. Instead, it needs to be funded properly, not just by the Americans and ourselves (the UK) but by the many other countries, which belong to it but make insufficient or late contributions.
Secondly, it is very good at stating problems, writing voluminous reports about what needs to be done but never taking action on the resolutions it passes or taking so long that situations are overwhelmed by events.
What happened with the Dutch peacekeepers in Bosnia when Vladic killed the innocents during the 1990s during the Yugoslav civil war is an example of the ineffectiveness of the UN and their inability to resource peacekeeping forces with sufficient manpower or firepower.
North Korea is poking its finger in the eyes of the Japanese who they hate with a passion for invading them and savagely mistreating their citizens and the hapless “comfort woman” who were often serviced by Japanese Imperial troops 22 times a day.
During the Korean War, the Americans used delayed action bombs so that people had to remain in their houses for days on end and 20% of North Korean civilians were killed.
The oriental concept of blaming current generations for what is in effect “the sins of their fathers and ancestors” is at play here so someone like the Chinese and the Russians need to be brought into the equation to get a deal done in terms of an uneasy peace and then act as guarantors under the auspices of the UN
Kim Jong Un is a psychopath and a dangerous man but we can understand why he mistrusts the West and is determined to keep nuclear weapons, given the fate of Gaddafi and Saddam Hussein. Like me and countless others, he can read the PNAC website and see that under the Wolfowitz doctrine his country along with Syria, Iran, Russia and China are all targeted for “regime change”. So convincing him otherwise is likely to be hard for any Westerner, even an elder statesman like Jimmy Carter.
He must first be contained then the country needs to be subjected to HAARP triggered earthquakes and flooding and then a long time after that we can eliminate Kim Jong Un using fully cloaked craft and Ironman suited special forces operatives with invisibility shields.
Dr Alf's Blog 
John, thank you again for sharing your views on North Korea.
With regard to the UN, I do not think it’s a question of funding and debt collection. The UN is riddled with corrupt politics. The UN is deeply biased towards the influance of the Arab League. Also there’s the political standoff at the UN Security Council between the five permanent members (US, UK, France, Russia & China). Then there’s the issue of effective stewardship of the UN and its agencies. There has been historical precedent of the US pulling out of UN agencies, where financial practices were questioned. Perhaps, countries that are delinquent debtors should lose full status and be relegated to associate status?
With Britain and France, weakened by domestic challenges, it’s hard to see them playing an effective role at the Security Council, so the UN gets weaker month by month.
As for US attacking North Korea, surely it’s a thin line between proportionate retaliatory response and an act of war?