I guess the trick is whether an Empire can evolve into something else. Whatever the rights and wrongs of Britain's Empire it ceased to be an Empire but became a Commonwealth. Either by force, resistance or experience (or good fortune) it became some thing no other empire managed. That's not to sing its praises just to say that America could become something other than a fallen Empire. I won't be pedantic and say it can't fall from something it isn't

Rome fell when the idealists emperors and senators were overthrown by the business men, speculators and accounts, then economics replaced pragmatism and empire fell.
Same thing happens with all empires.

Sound familiar

If you look at 'Empire' from position of our influence on global affairs the U.S. has certainly peaked in that regard. China will definitely become the world's largest economy in the not so distant future due to their ongoing modernization and they have more that 3 times the population of the U.S. I foresee a major realignment of alliances coming especially accelerated with the current America first push. For us living in the U.S. it's hard to predict what that means, but I think the political battle over the ideological direction of this country is just now really starting to heat up. Whether it turns ugly depends on the leadership we put in place.

It's hard to say either way. I think this question is for future historians to decide. All "empires" go through lower periods, some rebound. Some do not.

I think this is wistful thinking by some people. So long as America is the only power capable of projecting force anywhere in the world it will remain the dominant force in global politics. Even its main competitor in that regard, China, is seeking only to be able to project regionally.

As someone who lives in a declined empire (my childhood globe was 1/3 red). I can say it starts earlier than you think. Firstly you identify the peak, which in the USAs case was the end of WW2. The US was the sole nuclear power. Alaska and Hawaii had been incorporated into the states. It had been victorious in every war it had ever fought and consumer spending was on the up. Military spending did not go down however and the US remains the only economy to burn this candle at both ends. The resultant debt is something that drains federal spending each year. After the peak, the Korean war which ended in a draw. Then Vietnam sealed Americas decline. Oh there have been high points since, the moon landings and the collapse of the soviet union but the EU took the lions share off USSR empires carcass and never again will the USA be the invincible force that it once militarily or economically was.

It is clearly in decline and the open question is whether it will be a relatively orderly decline where the patient doesn't suffer too much and dies in his sleep, or chokes himself to death on the bedroom closet door handle, dying in a pool of his own excrement, etc.

There is too much of a drumbeat of disturbing developments, of long-standing perfidy breaking out unashamedly into the open, of willful ignorance and hatred winning the day, for me to believe any longer that we can recover from it.

If an unusually virtuous and competent leader were elected in 2020, I think it would only delay the inevitable.

At 61, I am probably going to stay here and gamble that I can get through what's left of my life over the next generation or less without experiencing a dystopian hellscape. But if I were any younger I'd be heading for someplace like New Zealand I think. Someplace that might hold on another couple of decades before catching whatever cold America has.

The decline started with the election of Reagan and has accelerated ever since.

Yes... And Trump is playing the part of Nero. We should be so lucky it end the same way! I'd cite mid 70's or 80's as the peak and we have been on the slippery slope down ever since. Wars that go nowhere and massive debt. Farming out our strengths to other countries. Corrupt politicians who let big corporations run us. It's not looking pretty.

Is it salvageable? Perhaps. Will it happen? Probably not. China will rise above us.

I think climate change, automation and globalization are the biggest factors in the decline or transformation that will take place in the not too distant future.

It is not falling in the sense that it will collapse, but other powers are rising that will challenge USA as hegemonic.
The doubt is how USA will behave without being the only big boy in the yard.

It currently is, but we haven't passed the event horizon. We can save her.