I have to disagree that no other rising power would pick up the slack. They would take it over and possibly change the name, is all. They are fine with the USA bleeding to death into the UN, and will not “step up” as long as the USA is doing that—after all, it is the work of the useful-idiot liberal fifth column in DC and it does not serve their interests to interfere.
You STILL have not given a solution. You say it must be destroyed but insist US leaving is not the answer. So WHAT is the answer to destroying the U.N. in YOUR opinion?