That’s just mindless contrarianism. There are plenty of successes of international cooperation. Of the top of my head: protection of the arctic and Antarctic, restrictions in the trade of ivory, tropical woods, big-game hunting (and trophies) etc. Lots of fishery agreements, nuclear testing ban, standards for offshore oil drilling, double-hull tankers etc.

That’s just the tip of the iceberg and only wrt the environment. EU and NAFTA are also international agreements that have teeth, as is the Berne convention on copyright (even if you don’t like it). Unicode is the UN in action as is the boat that will pick you up if you happen to get stranded on a deserted island (and have the necessary, and standardized, beacon). If you’re a Mongolian in a Mexican jail or a Mexican in a Mongolian jail, your embassy will be informed and allowed to render legal support, thanks to an international agreement to that effect. If you’re being subjected to cluster munitions, your foe is one of the few people on earth that wouldn’t enjoy a trip to the Netherlands. If you find yourself being extradited to The Hague, the plane you’re traveling on will conform to internationally agreed safety standards. A kilogram, meter, second, or joule is the same as your trading partners‘, thanks ISO, and the T in NATO seems to be some mighty piece of paper, considering how it manages to scare the shirtless man shitless.

Would you instead favor starting a war over this? Because this is reality, accords and treaties are tools of diplomacy and they are binding, you can sue other nations or implement other measures against them as a collective of signatories where without the accord you would act unilaterally and without cause.

I think you, like many, mistakenly assume that there is some law or authority over all nations.

Montreal Protocol worked.

What do you suggest we do instead?

better than nothing