I don't know when the US said it's unnecessary, but it certainly is unfeasible. Normally, when you are not solvent, you go to a bankruptcy court. The deal is that you accept the court's rulings and the creditors accept them too, and if anyone's unhappy, they can argue within the confines of the judiciary system, and the law enforcement is always present to make sure everyone plays nice.
None of these things exist in an international setting. And the most important missing piece is the law enforcement. If we set a bankruptcy court in Hague, let's say, and one of the parties does not respect its rulings, what exactly is the consequence? You can set up such a court, but it would lose its legitimacy in no time as more an more parties will disregard what it says.