Here's an interesting piece laying out some of the facts of UN dues for those who care. Things like the fact that the UN has no power to make mandatory any payments of dues; that the US has paid, without reimbursement, far more (perhaps 1000% or more in the past 10 years) on behalf of the UN than its total dues amount to; that many people disregard in this discussion the fact that the Constitution supercedes the UN Charter in how the US must act in regard to the UN and payments to the UN; etc.
Should the US pay more money to the UN? I don't know, maybe. But it might be easier to get it paid if people would start realizing that the dues are not an obligation and that the US, far from shirking its duty to the UN, provides more assistance to the UN than any other nation, by far.