1000 years from now, assuming records still exist, what do you think historians will give as the end date for the American Empire?

Sometime in the 2030's, I think.

The US isn't going to be irrelevant anytime soon, but this Presidency is doing an immense amount of damage to our soft power and influence that we might never recover from. We'll hold on for a while probably. China is expanding their influence over the Pacific, and I think their global influence will only increase over the coming years. Europe will probably strengthen as well, assuming they can weather this kind-of, Russian sponsored, Right Wing, authoritarian insurrection type thing trying to take root. 15-ish years sounds right, for somebody else to take the spotlight.

That's an interesting question.

One famous empire, the Roman Empire, has a few endpoints. However, as you point out, it's commonly accepted that the Western Roman Empire fell in 476 A.D.

But... this overlooks one big point: Rome had been falling for centuries before that. It had been sacked four times in the century leading up to 476. How were the Gauls, the Visigoths, the Vandals, and the Ostrogoths all able to sack a city that had stood for over 1,000 years and, at one point, ruled most of the known world? The rot had obviously set in a long time before that, or these invaders would have been repelled. Look at Carthage's attempt, led by Hannibal, to attack Rome in 218 B.C. And the march of the Germans on Italy in 102 B.C. Both attempts were repelled by a strong Rome - a pre-Empire Rome, even! And there were no attempts on Rome for centuries after that, because it was buffered by all its territories. But in the 5th century A.D., four tribes of barbarians were able to march through Gaul, and through Italy, to sack Rome. The rot had obviously set in a long time before.

One point that could mark the beginning of the end is 286, when Emperor Theodosius I Diocletian decided to divide the Roman Empire into two administrative areas: a western and an eastern area. This was an admission that the Roman Empire was now too big to be ruled by one person or from one city. As if Roman politics weren't complicated enough, there were now four rulers: two senior Augusti and two junior Caesarae (one Augustus and one Caesar in each half of the empire). This just increased the in-fighting among the Roman elite, leading to the fall of the western half two centuries later.

Then there's the British Empire which didn't end so much with a bang as a whimper. It just sort of faded out. In 1876, Queen Victoria was crowned Empress of India. Half a century later, in the 1920s, the British Empire ruled over a quarter of the world's population. By the end of the 20th century... there was no British Empire to speak of. But there was no single event to point to and say "that was the end of the British Empire". Some people point to the hand-over of Hong Kong back to China in 1997 as the end, but the British Empire hadn't truly existed for a long time before that. In the 1980s, many of its former colonies (Canada, Australia, New Zealand) severed their last constitutional ties to the UK. In the 1960s, its former colonies in Africa became independent. India, the jewel in the Empire's crown, had become independent in 1947. And all these can be traced back to World War II, which left Britain broke and severely damaged. But the roots of World War II can be traced back to World War I, which itself can be traced back to the rise of Germany in the late 1800s. So when did the British Empire end? We don't know.

The point is that, while there might be a big event which marks the end of the American hegemony (I wouldn't describe it as an Empire), that event will only mark the end of a long process of deteriorating power. That process is happening right now, but it's hard to predict what will mark the end, and it's also tricky to agree on when it started.

Did it start in 2001, with the terrorist attacks on American soil? America has floundered a bit since then. The current incumbent isn't the first U.S. President to go rogue - George W Bush flouted international law and the United Nations when he and his "Coalition of the Willing" (a whole three other countries!) invaded Afghanistan in 2003. And that invasion has been a massive failure. Every American military action in the Middle East since 2001 has demonstrated that the USA can't simply stamp its foot and get its way any more (if it ever could). Was 2001 the beginning of the end?

Or was it 1989, when the Berlin Wall fell? That event was described at the time as "the end of history", when the forces of democracy and capitalism had finally outlasted all competitors. Except that it wasn't true. However, without a strong opponent like the USSR to define itself against, the USA has struggled to find its way.

Was it the Fall of Saigon in 1975, when the U.S.-backed forces of South Vietnam finally lost the Vietnamese War?

We don't really know.

What will the end look like? I don't know that, either. But it has certainly already begun.

The day the US defaults on its debt.

An exact date is impossible to predict, but I believe we've passed the point of no return. The national debt will keep increasing, year after year, and with it the interest payments. Eventually the big credit rating agencies will downgrade the US debt, and interest rates will spike. That event will mark the beginning of an ever worsening debt spiral, until one dark day, the US government decides not to pay. That's the day historians will consider the end of the US Empire.

So when will it be? Hard to say. I believe the credit rating downgrade will take most by surprise, and could be as soon as the next decade. Or maybe as late as the end of the century.

The result will be a global financial crisis to rival the Great Depression. A scaling back of US military and diplomatic operations will erode its power and influence around the world. Mass unemployment will lead to increase in crime and civil unrest. Another demagogue might rise. States may try to secede in an attempt to escape the crushing debt. The US will never regain its former power and glory.

This is all speculation of course, and it's more likely to be wrong than right. I just felt someone should mention the debt default scenario.

I think the watershed moment where the American Empire stops to exist is the day that NATO goes. Whatever happens next, the U.S. will no longer be in a position that it dictates international geopolitics.

The current POTUS is stepping on the accelerator down that slippery slope, but judging by the incredible amount of pushback he gets from his own Cabinet, I'm guessing this won't happen for a few decades yet. But I'm pretty sure historians will look back on this moment and describe it as a harbinger.

There are really at least two questions bundled in this, I think.

The first is the end date of the United States, and the second is the end date of the American Empire. The first I view as a more political question - the American Empire could well go on after the end of the United States, in the same sense that the Roman Empire went on well after the end of the Roman Republic. This would be some sort of major change/overhaul of the political system that could not have been accomplished legally under the framework of the original system. It would probably be dated based on a significant tipping point event (i.e. the president issues a decree dissolving/federalizing all the states and has all the governors arrested) or possibly based on the date a significant figure was elected or rose to power (i.e. General So and So was sworn in as some sort of emergency Commander-in-Chief on a particular date, for the duration of an emergency that never officially ended).

The end of the American Empire might be the same date, but could also be different by several centuries. It would probably be dated based on a major territorial loss, particularly the loss of the capital, or territorial dissolution (i.e. various states come together through some political process and agree to dissolve, perhaps with some hold-outs ineffectually claiming to be the true successors).

It's really difficult to, say, though. Going with some of your examples: in 1204 you have Constantinople captured by foreign invaders. Emperor Alexios V flees, is captured, and executed. There are three rump states all claiming to be the legitimate empire. But we don't date 1204 as the end of the Byzantine empire, because they manage to put together a successor polity that can credibly claim to be such, and lasts another two centuries.

Well...with Trump, but honestly it could be a couple decades after that. I think our grand leader is a turning point. I think that it will happen sooner in a hundred year span than later d/t tech comm.

"The ultimate “dirty old man,” Tiberius succeeded Augustus, Rome’s first emperor...,"(www.walksofitaly.com) .

It is hard to predict because these times are different from 1000 years, or even 100 year ago. We've progressed so incredibly far, I think the turn-around for decline/revolution is fast approaching... so this is just an opinion...