It's not about the UN imposing its will/mandate upon the U.S. It's about the hubris of not one but two Presidents making an end run around the constitutional amendment process in order to avoid Supreme Court scrutiny and half of the legislative body.
What's necessary, in my opinion, is a REAL constitutional amendment which will, once and for all, make it ironclad that no treaty, under any circumstances, can suborn rights guaranteed under the constitution nor abrogate our national sovereignty to any international body. Get that? You don't have to worry about nefarious treaties such as this.