Commenting on a months old thread is bizarre, but seeing as you never got an answer, and I have a history degree, I’ll give it a shot.

Ratification of a treaty in the US requires a two thirds majority (67 votes) in the Senate. Nowadays that would be nearly impossible to muster. On a closely related (and therefore relevant) topic, part of the reason why US politics is so paralyzed is because a very narrow majority of the Senate still clings to procedural rules that effectively requires at least sixty out of one hundred Senators to agree to pass legislation. This is known as the legislative filibuster, it’s not required by the constitution but until recently both parties uniformly defended its existence for their own purposes. Now only the GOP and two recalcitrant Democratic senators defend it, but that’s enough to block reform for the time being (the Senate is currently divided 50-50 with the Vice President being the tie-breaking vote which gives the Democrats a razor thin majority). My guess as to why the Democratic Party stopped defending it is because it eventually dawned on them that so long as it exists there is literally zero chance that anything substantive will be done about climate change in this country. But it isn’t even just about major policy changes, the list of seemingly reasonable crap we can’t get just ten GOP senators to agree with is almost comical. The Senate already isn’t a truly representative or democratic body, it was never meant to be, and despite the delusions of some activists and certain subreddits, it never will be. Requiring a supermajority for something (whether it be treaties or legislation), therefore increases the undemocratic nature of what is already an undemocratic system by design. All that being said, seeing as the US is a federation, it does make sense for there to be geographical consensus about the treaties we ratify.

With all of that in mind, the reason why the US hasn’t ratified any of these treaties is because the GOP, or most of it, opposes them for one reason or another. They are uncomfortable with the very idea of treaties that are not obviously and directly related to international issues. They believe such treaties circumvent the constitution insofar as they are even constitutional in the first place. They reject the idea that the UN should make binding rules concerning the rights of women and children or anything else that they perceive as being within the purview of domestic law. It is an aspect of globalization that they are opposed to. There are specific reasons why they don’t like certain treaties as well. They were afraid about CEDAW creating a legal right to abortion and the CRC restricting parental rights. Still, if you think this aversion to internationalism sounds odd for the party that gave us George W. Bush and Ronald Reagan I wouldn’t blame you, but even in their time, Ronnie and Dubya were both internationalists compared to the rest of their political party.

A somewhat more valid reason why the GOP doesn’t like international treaties is because of the differences between the judiciary of our country versus those of other countries. Other countries have no problem with vague treaties, in fact they love them. They get to say they’re doing something without actually doing anything! Wonderful ain’t it? They probably think so. Well, it’s a lot less likely to work that way in the US. The judiciary is a separate and powerful branch of the government. There’s nothing stopping this Supreme Court or a later “activist” Supreme Court from interpreting a vague treaty in a way that would be deeply unpopular, and making it the law of the land (as if it were the executive or legislature). This is related to the final reason why the GOP dislikes international treaties, in their view, the vast majority of these human rights treaties are dead letters which are ignored by the majority of the nations which ratify them. In their view, they are simply being honest about rejecting them. Do you actually believe that the Islamic countries are enforcing CEDAW? That Latin American countries are enforcing the Indigenous and Tribal Peoples Convention of 1989? That any countries outside of Scandinavia are enforcing ICESCR? Because if you do, then there is a bridge in Brooklyn that I have that you might be interested in buying. Some countries may even think they’re actually enforcing these treaties, but the GOP would say that this is bullshit, since they’re not being enforced as strictly as an “activist” US judiciary would enforce them. In any event, us ratifying these treaties won’t change anything outside the USA and the GOP (rightly IMO) doesn’t trust the international community to enforce them outside the developed world. The reason for this, is because the GOP firmly believes that the majority of the international community is irredeemably anti-American and dominated by hypocritical “post-colonial” radicals whose goal is to impose idealistic, unrealistic and burdensome international human rights treaties on the developed world, while consciously allowing the developing world to “benefit” by completely ignoring said idealistic and unrealistic treaties.

As for why the US enforces a few treaties we haven’t ratified, it’s uncommon for us to do so. The reason why we try to enforce UNCLOS specifically is because we are a signatory and almost all of that treaty is already codified in US law. The only disagreeable part of UNCLOS for the US are its provisions about deep sea mineral resources. In contrast to countries like Turkey, the US accepts everything else, or nearly everything else, in that specific treaty as binding unto itself.