Even though UN resolutions are and always have been meaningless, they can still apply some pressure.
Fun fact: the UN created the International Criminal Court to prosecure war crimes, something the US vehemently opposed. The US under then-president George W. Bush, argued that such a court may lead to US servicemen being charged with war crimes. Of course the US has committed war crimes [1]. So Bush passed the Hage Invasion Act [2], which authorizes the US to invade the Netherlands if any US servicemen are brought up on war crimes at the ICC in The Hague (in the Netherlands, obviously).
The point is the US wouldn't do this if the UN could be completely ignored.
There are several major countries that have varying degrees of harsh long-standing sanctions at the behest of the US that are completely unjustifiable:
1. Cuba. Why? If you look beyond the "communism = bad" kneejerk reaction you come to the justification that Cuba nationalized assets of US citizens. That didn't stop the US seizing Afghan citizens' assets [3];
2. Venezuela. Why? Because Maduro started to or threatened to nationalize their oil industry. So the sanctions were really for the benefit of Chevron, Shell and Exxon. There's no principle here. The US had no problem with Chavez (who was awful). But again, "communism = bad";
3. Russia. This one makes sense. I mean the average citizens will bear the brunt of this but Russia started an unjustifiable war in Ukraine so what else can you do?
4. Iran.Why? After the US backed a coup of Iran's democratic government to install the US-allied Shah (again, communism and the Truman Doctrine comes into this), which pretty much sowed the seeds fo the 1979 fundamentalist revolution, which has been the government since. We've decided to pick sides with Saudi Arabia. Nevermind that Saudi Arabia funded and supported the 9/11 terrorists (and the madrasses that created them) and is currently engaging in a genocide in Yemen with US weapons. Sanctions seem to have the effect of solifying support for the regime (up until recently). Obama brokered a deal to end this. Trump blew it up essentially to appease Israel (and Biden has continued that policy).
4. North Korea. Does anyone stop and think why North Korea is really under heavy sanctions? "Because they're bad" is really the crux of this. The implicit assumption here is that US is "good", somehow by definition. That belief creates all sorts of problems.
Consider this: Cuba produces a lot of cane sugar. The US spends a lot of money on the corn lobby and corn (in the form of high-fructose corn syrup) is a common cane sugar substitute in the US and almost nowhere else in the developed world.
It's kinda weird how so many of these sanctions can be tied back to US economic and political interests rather than any form of principle.
[1]: https://en.wikipedia.org/wiki/United_States_war_crimes
[2]: https://www.hrw.org/news/2002/08/03/us-hague-invasion-act-be...
[3]: https://www.nytimes.com/2022/09/14/us/politics/afghanistan-c...