You'll be able to find more information on this elsewhere, but let me just sum it up and point you to the more detailed writeups.
There's a UN treaty, the U.N. Convention on the Rights of Persons With Disabilities, that just came up in front of the lame-duck Senate. It is heavily modeled after the Americans With Disabilities Act, and has been ratified by 126 countries, including the other four permanent-veto nations, and signed by 155. (Most of the non-ratifiers are in Africa, as well as Venezuela, Afghanistan, Iraq and North Korea.) The United States, already a signatory, voted today on ratification, needing 67 votes to do so. Seeing as it not only required the United States to do absolutely nothing it wasn't already doing, but was modeled after things the United States is doing and for all intents and purposes told the rest of the world to be more like the United States, this should have been a no-brainer.
The treaty failed, only gaining 61 votes. 38 Senators, all Republican, voted against the treaty, which was negotiated by Bush 43 and walked past 1996 Republican nominee Bob Dole, who was sitting in a wheelchair, on the way to vote against it, because- I am not making this up- they feared it would threaten American sovereignty. They literally rejected a treaty modeled after American legislation because telling the world to act more like America was a threat to America.
If your brain just broke trying to make sense of that, don't worry, because everyone else's has too.
Rick Santorum- not a Senator anymore- argued that it could be used in American courtrooms, which is wrong, because only American law can be used in American courtrooms and this is American law anyway. Jim Inhofe- who is a Senator- argued against "cumbersome regulations and potentially overzealous international
organizations with anti-American biases that infringe upon American
society", ignoring the fact that the regulations do not encumber or infringe upon American society in any way because the treaty was modeled after American law which is a really funny thing for an overzealous anti-American organization headquartered in America's largest city to do, don't you think?
Though really, when America acts like this, who would want to act like us anyway?