A significant segments of the population in US no longer believe that the government has their best interest at heart, and that's a measure of how far the collapse of US empire has progressed. The underlying cause for this mistrust is the decline of material conditions over the past several decades. This trend accelerated in particular with the fall of USSR as detailed in this excellent essay by Michael Parenti. However, most people in US lack the political or economic education to understand what's happening leading to public lashing out in random and irrational ways. People understand that they're being hurt, but they don't understand who is responsible or why it's happening.
Loss of public trust in the government means that US is now locked into an irreversible decline. The mainstream is split across political lines, with democrats and republicans simply blaming the other tribe for all the ills in the country. This creates a political climate that's ripe for opportunists like Trump and Biden to game leading to further deterioration of living conditions. The country ends up in a worse state after each successive election cycle, and the sectarian tensions continue to become more prominent. Violent outbreaks are starting to happen already, and I expect these will only get worse going forward. In fact, a model US themselves produced is predicting collapse and a likely civil war in the near future.
Furthermore, the effects of the collapse are not evenly distributed. While many working class people experience significant effects personally, nothing has really changed for the policy makers. This creates a lag between problems occurring and the leadership becoming aware of them. Thus things have to degrade quite significantly before people in power become aware of the severity of the problem.
On top of that there is the problem of climate breakdown. A river in Colorado that around 40 million people rely on is drying up while California is running out of fresh water as well. Heatwaves resulted in massive crop loss this year. Then there were megafires, hurricanes, and other extreme weather events like Texas cold snap. All of this is putting stress on the failing infrastructure and straining supply chains to the breaking point. As a result there are already shortages of essential goods.
We'll see more extreme weather events and of greater intensity each and every year going forward, and it's clear that US lacks the capacity to react to these problems in a coordinated fashion. All it will take is a single extreme weather event, such as a heat dome that lasts a few weeks, to cause a famine. And historically that tends to be the breaking point. People can put up with a lot, but there's really nothing left to lose when you're literally starving to death.
The further along collapse of the empire progresses the more difficult it becomes to arrest it. Halting and reversing current trends requires honestly acknowledging root causes of the problems in order to take corrective action. However, existing political climate precludes this from happening as was illustrated during 2020 election. Sanders proposed sound and necessary policies such as The Green New Deal, public healthcare, and student debt forgiveness. However, a candidate committed to continuing the same destructive policies that led US where it is today won instead.