A very good reason to leave the UN.
You're absolutely correct, it is vitally important that the United States prevents international election monitors from observing American elections.
The United States should withdraw from the United Nations, because the OSCE (a body which is neither funded, nor takes direction from, the UN) is going to conduct election monitoring in one of its member states - an action it has engaged in in its member states for many years; an action it has engaged in in the US on a number of previous occasions (and actually welcomed by administrations under both parties); an action the US agreed to explicitly by virtue of assent to
the Paris Charter (1990).
That the UN hasn't intervened to stop this travesty is truly shameful and appalling. Withdrawal from that organisation is therefore a perfectly reasonably and proportional response. (Presumably seeing as how the OSCE is the actual organisation that has approved, organised and funded the monitoring, their HQ should be blown up or some such, amirite?)
By denying international election monitors the right to observe American elections (in line with the principles of the OSCE Charter agreed to by the US), the Amercian Government can send a strong signal to marginal democratic regimes around the world that foreign observers are actually a danger to democracy and should not be tolerated - even after the Government has committed by international agreement, and through past practice, to allowing such observers.
Kudos to you JJ on yet another cojent and insightful contribution to the Forum.