The correlation I see with Rome (and which could be applied to so many other empires) is that people, and in particular the elite gave up on the project of state. This was the case both when the republic shifted to empire and also when the western empire collapsed. ‘Rome’ at this time was just the status quo that let the elite ransack wealth, it didn’t mean anything beyond that, there was no more willingness to sacrifice to or even value the ideal it represented. So in the US nowdays with neoliberalism the same sort of process is taking place. Instead of ghouls that are nonetheless statesmen who basically want to preserve and strengthen America you have failsons and madmen but also intelligent people who nonetheless recognise the way the wind is blowing and that now is the time to fill your pockets rather than dream big. And of course the working class is also losing faith in the national ideal too, and when the Goths ransacked Rome it was because there was no-one left to defend it because everyday Romans just refused to serve in the military. And they refused to serve because there was no point, and when Rome collapsed, initially at least life actually improved for a lot of the working class and it didn’t even change that much for a lot of the elites either, other than they had to call the barbarians boss instead of the emperor.