Afghanistan's reputation of being the Graveyard of Empires is actually a new thing.
You could say it started with Mahmud Hotak in 1722, when his Afghan army marched into Persia and ended the Safavid Empire.
Next came the British.

The most iconic moment of the Anglo-Afghan wars was the total annihilation of 4,500 British soldiers and 12,000 civilians in January 1842, during their retreat from Kabul to Jalalabad. Only a single wounded surgeon riding a wounded horse made it.
However, it didn't end the British empire in any way. The British invaded in 1870's, and this time their conquered Afghanistan, albeit not easily. Then in 1919 there was a third Anglo-Afghan War, in which the British won all the battles, but in the end they decided to simply cut and run.

The Soviets were next. After 10 years of fighting they withdrew in failure, and two years later their empire vanished.

“Since the Soviet army was the glue that held the diverse Soviet Republics together, its defeat in Afghanistan had profound implications for the survivability of the Soviet Union,” they write.
...
“The Soviets withdrew because Afghanistan became an increasingly expensive proposition for an empire that was crumbling from within,” Manchanda writes in her book Imagining Afghanistan.

I think that it is fair to apply both of those descriptions above to the United States today, but with modest changes.
There's been a lot of comparisons between Kabul in 2021 and Saigon in 1975. However, there are at least as many differences as similarities.
For example, the U.S. lost in Vietnam when our enemy was heavily supported by Russia and China. The Taliban beat us without any major allies. Then there is the status of the U.S.

The US was utterly dominant both before and after the blunder in Vietnam. Even after that blunder, the world was still divided between the winning West and the remaining Rest. Prosperity would still be primarily found in New York, London, Berlin, and so on.
That is no longer the case. The fall of Kabul was symptomatic and a product of the decades-long process of the severe weakening of American power, authority, legitimacy - in short, its hegemony.

Think of it this way. At the beginning of this century, America was dominant economically, militarily, and culturally. We actually had some claim for moral leadership.
Our moral leadership started to come apart when the US invaded Iraq in 2003. We not only disregarded the U.N. but also propagated lies about Saddam's WMDs.
Then the credibility of our economic order collapsed when major US financial institutions imploded one after the other in 2008 due to massive fraud.

One of the last elements of the American empire still functioning was the military. A military that just got beat, not because of the weaknesses of the soldiers, but because of the corruption and incompetence of our leaders. In other words, the same factor that caused all three of the failures.

So let's add this up. We've lost our moral authority because our leaders lie, cheat, and steal, and generally act like jerks to our allies, while being bullies to everyone else. Because we have no moral authority, we no longer bother with 'soft power' and diplomacy.
We no longer have an industrial base because our corrupt ruling elites have exported all of our industries overseas. Plus, the ruling class has become predatory monsters that are gutting the working class, and in doing so is weakening the general economy. Thus we are in the process of losing our economic influence.

This leaves our empire resting upon two things: the U.S. dollar and our military.
The strength of the military rests on the dollar, and vice versa.
We can force the rest of the world to use our dollars because of the strength of our military. We can afford such a huge military because of the strength of the dollar, which allows us to borrow so cheaply.
It's on this fragile edifice that America's empire rests. Which is why the events of 2020-21 bode badly for our empire's future.

A lot of people on the internet will tell you how deficits/debt doesn't matter.
They're wrong, sort of.
The debt doesn't matter as long as everyone else in the world still accepts our dollars and uses them as a reserve currency.
But if the world start to question the value of our dollars, then those debts/deficits will most certainly matter! Doubt means risk, and risk means much higher interest rates. When there is already a mountain of debt, it wouldn't take interest rates to rise a lot before the U.S. would have no choice but to default.
Why would other nation's start questioning the value of our dollars? One of the reasons would be the loss of the ability of our military to intimidate the rest of the world.

At the same time, there is a collapse in faith in neoliberalism that is undermining the legitimacy of the ruling elite as well. No alternative system has arisen to take it's place yet, but that doesn't mean that everyone isn't coming to grips with the idea that the Reagan/Thatcher economic empire has failed and is coming to an end.

After it became obvious that we lost the Vietnam War, the United States was hit by a surge of inflation and a significant decline in the U.S. dollar.
This is despite having both the globe's strongest economy and strongest military. We had still had a middle class and an industrial base, and the government sometimes even cared what working class people wanted.
None of those things are true today.
Would a surge in inflation and a significant decline in the U.S. dollar be much of a surprise in the next few years?