I tend to think the empire in general is screwed, but try not to overstate it cause obviously it can still do a lot of damage on the way out, especially to materially weaker countries.

But like, the current trajectory seems like one in which things are going to keep snowballing. The backfiring war against Iran is probably going to be seen as a turning point by historians looking back, but there are other factors too. Like the state of the environment, as you point out. The de-industrialization/financialization of the economy that left them vulnerable to exactly the sort of countermeasures China is employing in limiting their access to certain materials. The ideological and intellectual regressions, including the nepotistic handing off of power to failsons who don't understand the subtleties of the psychopathic, but nevertheless thoroughly plotting, neocons who came before. The fundamental overextending that empires are prone to, leaving them with too many fronts to manage in a world that is increasingly materially capable of, and ideologically interested in, moving on without them. The counterexample of a better world being possible without them, lead by China, while the empire increasingly looks old and decrepit by comparison (sometimes literally), even within its own borders; the US won't even guarantee its citizens healthcare, the EU is unequipped to handle rising temperatures due to climate change, things like that, that illustrate how the empire is not only behind China, it's actually decaying more than it is growing.

The empire is being led by enormously entitled people who believe that belligerence is the same as structural power and it will only keep working as long as they hold onto some amount of structural power that others built before them. But they are already squandering it, as we see in Iran, because, on multiple levels, they don't understand how to build anymore.

Meanwhile, China, the factory of the world, understands building better than they ever did and is not wasting time in using that capability to piece together an alternative world order, where sovereignty actually means something.