I get that collapse is a slow ongoing process but when the history books are written, what do you think will be considered the US' own Battle of Ravenna? What will occur that historians can point to it and say, "this was the effective end of the American empire." ?
Empire collapses from the periphery inwards. As the colonial holdings cease to turn out super profits, the exploitation will return to the core and the reserve army of labor parked in managerial positions will be liquidated to fill the vacuum of productive/manufacturing labor.
The conflict between the international bourgeoisie and the petty bourgeois middle class will elevate into some form of civil war as both classes fight over who gets to profit off this shifting status quo and as usual the proletarians and those drafted into the proletariat from the managerial reserves will be used as the tools of this conflict.
Wars will continue to break out both within and without of the core as an attempt to regain colonial super profits and maintain profits using domestic labor.
None of this will be overnight (aspects of it will be, like Iraq and now Ukraine), but a long simmering collapse over the next 100 years or so.
The core cause being the inability of capitalism to maintain social order as it is inherently cannibalistic and destroys the environment and social fabric that it's profits are drawn from. Any "events" that occur during the collapse are just symptoms of the primary contradictions between capitalism and it's own source of profit.
All I can pray for is that this is the last empire- that the age of martial, colonial and economic domination will finally come to an end, and we can just... be people.