Media playback is unsupported on your device Media caption Is the US in terminal decline? Watch Mark Mardell's full report from North Dakota for The Editors programme

It is eerie to walk so close to a weapon of mass destruction.

The B-52 bomber is one of the ultimate expressions of American power. If the president decides to drop a nuclear bomb, this is the sort of aircraft that would do it.

I am careful not to step over the red line around the plane. A sign painted on the ground warns lethal force can be used against those who cross it without authorisation.

I've come to Minot Air Force Base in North Dakota, filming for the new BBC One programme The Editors.

The programme aims to get the BBC's on-air editors to explore - and hopefully answer - a big question. My chosen subject is the decline of American power.

There's little evidence of it at the base, where the sign above the gate reads: "Only the best come North".

An old Minute Man missile stands to one side of the entrance.

The road names here are a testimony to the base's purpose - Ballistic Avenue and Cruise Missile Lane. It is home to two arms of America's nuclear strike force, the Fifth Bomb Wing - known as the Warbirds - and the 91st missile wing, the Rough Riders.

As I talk to a group of very normal, bright and cheerful men and women from both units, I am awed by the potential nature of their job.

I joke that when things are really stressful and going very wrong, some people in my business say: "It's only television." They can hardly say: "It's only nuclear war."

As well as confidence in their routine and their abilities, they have faith in the nature of American power. They all stress that their job is deterrence. They hope these weapons will never be used.

But I put it to Capt Kim Brown that she would be the one to pull the lever, to drop the bomb.

We are still a good Christian country... I have faith in the President and all my leadership Chris Duff, Air Force captain

"As the offence team we are responsible for weapons activity... dropping the right type of weapon on the right type of target," she says.

"That's quite a responsibility," I say.

"It is," she replies. "But it's what my nation asks me to do. It's my job, and I trust those above me that they are well-informed to make those decisions."

I ask Capt Chris Duff about the responsibility.

"It is one I embrace. It is what I signed up to do," he says. "If it is called upon I will do it."

He is confident America acts for good in the world.

"The US obviously spreads democracy throughout the world, it's been proven to do that," he says.

"We are still a good Christian country. I am a Christian and it is founded on Christian morals. I have faith in the president and all my leadership."

Capt Duff was born in Liverpool and his parents were English. He chose to become an American. Does he think his adopted home is as great as it once was?

"I'd say yes," he answers. "This jet has been around for 50 years. It is still capable of reaching out and touching anyone in the world at anytime, should the need arise."

Decline paranoia?

Not everyone back east is so confident. In the four years I have been based in Washington DC, there have been a flood of books and articles on the decline of American power.

Perhaps Americans fretting about their place in the world is nothing new. There was the "Sputnik moment" in 1957 when the US thought there was firm evidence that it was being out-stripped by the Soviet Union. There was the fear of Japanese economic dominance in the 1980s.

The Editors Watch Mark Mardell's report from North Dakota as part of an episode of The Editors presented from Washington on BBC1 at 23:25 BST on Monday More from the programme

My colleague Kim Ghattas, in her book The Secretary, highlights this quote from Charles Dickens's Martin Chuzzlewit.

"Martin knew nothing about America, or he would have known perfectly well that if its individual citizens, to a man, are to be believed, it always IS depressed, and always IS stagnated, and always IS at an alarming crisis, and never was otherwise; though as a body they are ready to make oath upon the Evangelists at any hour of the day or night, that it is the most thriving and prosperous of all countries on the habitable globe."

But this time it is different. There can be no doubt America is in relative decline. Its economic and diplomatic power are not what they were. And there is no doubt it bothers many Americans.

For a while, everything was bigger in America - from skyscrapers to the sky, from the dream to the nightmares. The manifest destiny of expansion to the West perhaps gave rise to the illusion the horizon was endless.

But there are others with new frontiers now, and America's world is shrinking. The biggest economy in the world now has the biggest debt in the world.

This plays into an odd insecurity - in a country famously ignorant about abroad there is a curious stress on the very word America: American idols, American heroes, American dreams.

For it is a young country, still creating itself, reassuring itself that it is special, indispensible. Those who are aware of it may be hurt that they are not loved - and that hurt is most easily assuaged with bombast and swagger.

Belief in the notion of decline can be encouraged by both political parties, even as they trumpet America's superiority.

By around 40 AD a canny Roman might have predicted the Empire's decline. But it took another 400 years to fall

The Democrats believe America is falling behind in economic terms because of a refusal to invest in the infrastructure - and it really is crumbling; in some places it feels more like the developing world than Europe.

They would launch a taxpayer-funded crusade against decline, against poor education, a drive to create more talented graduates and invest in the technology of the future. That is one vision.

The Republicans' case is perhaps more interesting, more romantic, and more specifically American, although not necessary more true.

They warn America is growing away from its constitutional roots, doomed to decline by debt and outsized government.

In this vision, it can only save itself by being true to its destiny. It must want to be not only a power, but the power in the world, assertive, a leader, and if necessary a warrior nation once more.

Shifting power

But in large measure, the reality of decline that it is part of a huge historical re-balancing act - something we acknowledge in words like "globalisation" or "Brics", while often ducking just how profoundly the world is changing.

The model we in the West grew up with - and our great-grandfather's parents grew up with too - turns out not to be immutable.

Remember, wealth and power were pretty evenly distributed in the world until around the 16th Century. The rise of the British and other European empires, with their technological and ultimately military superiority, threw the world out of joint.

The US was heir to that, with the added power and zest of its expansion. In two world wars American intervention was decisive. Without its political commitment much of Europe would have been behind the Iron Curtain, and arguably the Cold War would have been lost.

At the same time a dream was coming true in the US: prosperity that spread to a huge middle class.

It is important not to be too rosy-eyed about this; poverty and discrimination were also present on a monumental scale. But it led many Americans to see themselves as the end product of Western democracy.

Perhaps they were.

Now the world is rebalancing - power and wealth will become more evenly distributed across countries. So yes, China will rival the US, and so will others.

But let no-one mistake how far above the rest of the world the US has risen.

The new 'Wild West'

It would take a lot - a catastrophic event - to dent the most powerful military the world has ever known - especially when the US spends more on its military than the next 12 big spenders. That's more than China, Russia, the UK, Japan, France, Saudi Arabia, India, Germany, Italy, South Korea and Australia added together.

It takes time for that sort of power to erode.

But military might does not stand alone. China's Chairman Mao said that power grows from the barrel of a gun, but guns cost money - power perhaps grows from a fistful of dollars.

And the American economy too has felt severe shocks recently. It will probably not remain the biggest economy in the world - some predict China will overtake it in three years' time.

Image caption The Bakken oil field has fuelled a new boom town

I drive on, through the land that was the Old Wild West.

I am sure that it was in part that sense of spreading across a huge continent, the possibility of seemingly endless expansion, that gave America the feeling that there were always new frontiers to conquer.

Perhaps the daunting climate and the constant attacks by those who originally lived on this land heightened a sense that the world was a hostile place that had be wrestled into submission, that justice was rough or not at all, that violence was the answer, that when the chips came down you were on your own as well.

Now horizons and old certainties are shrinking.

But much of North Dakota is still empty, and it still feels like the barrens.

Williston seems like a gold-rush town. It is the base for the exploration of the Bakken oil field, the biggest in the US. It has been made possible because of developments in fracking - the technology that uses pressurised water to pulverise the rocks and force them to yield their treasure of oil and gas.

The town has quadrupled in size recently. After travelling for hours on nearly empty roads it is a shock to be hemmed in by huge trucks thundering past on every side.

Everywhere signs flash "For hire". Ramshackle buildings look as if they have sprung up overnight, offering BBQ or a place to stay.

Local legend says it cost more to rent a house here than it does in Manhattan. The state has the lowest unemployment in America.

Image caption "America's day is still coming," says oil industry consultant Kathy Neset

"If you can't find a job here there's something wrong with you," a truck driver tells me, sitting high in his cab about to deliver the special liquid that drives the fracking process.

On the edge of town there are "man camps". They have been formally renamed "crew camps" in the interests of equality, but the new name hasn't stuck.

Hastily constructed to house all the transient workers, they don't feel like Dodge. They are rather nice, spotlessly clean with neat rooms like student dorms. But they are testimony to the fact there is money to be made here.

The source of this newfound wealth is celebrated in the jewellers on Main Street. The window is full of pen holders, desk clocks and ornaments, in gold, all in the shape of oil derricks.

The 'next frontier'

Fracking is hugely controversial, both for its impact on the local environment and CO2 emissions. But it is here to stay, and it makes a real difference to America's future.

The projections are that the US will be energy independent by 2020. All that cheap energy is already having an impact, one of the factors behind the return of industry to the country.

Standing next to huge "nodding donkeys" that suck the oil from the earth, I talk to Kathy Neset, who has worked in the industry since the 1980s as a consultant. She's a geologist by training.

"These wells right here are producing something like 800 to 1,000 barrels a day, for each one," she tells me.

"That oil is about two miles under our feet and I anticipate it will last for another 20 to 30 years. That is our energy security. "

She thinks this is evidence of America's future:

"I think our country is going up, up, up. The potential is shown right here in North Dakota."

But hasn't America, like the British Empire, like the Greeks, had its day?

"America's day is still coming," she insists. "We are on the upswing. And this is a perfect example of how American ingenuity is taking us on to the next frontier."

"We continue to reinvent ourselves... We have a new frontier, this oilfield, but we would be very short-sighted if we said this is the best we can do. There are more frontiers."

There will be many Americans who agree that their country has an endless appetite to pick itself up, dust itself down and reinvent itself.

At the end of my journey I find myself unable to give a straightforward "yes" or "no", as the programme would like.

Instead I have a series of reflections on the decline of America.

There can be no doubt the "rise of the rest" will make America shake on its pedestal, but whether it knocks it off is up to Americans themselves, and whether they can adapt to a new status, a somewhat lower place on the greasy pole of world power.

The colossus will no longer effortlessly bestride the world; that does not mean it will not stand tall.

They should not underestimate the importance of soft power. All over the world granddads and infants, jihadists and dictators, wear jeans, America's off-duty dress of choice.

That may sound trite, but the fact the world increasingly looks like America is important. Rock and rap, the English language and Hollywood and still dominate popular culture.

Those defenders of America who attack knee-jerk anti-Americanism are rather missing the point. Those all over the world who might say they are anti-American don't hate Jimi Hendrix and Woodie Guthrie, Levis and denim, Andy Warhol and Jack Kerouac.

They don't, usually, hate freedom or democracy, but a certain cynical exercise of America power sheltering behind those values.

It is important to remember America is still a very young country, with very bright dreams. It's a teenager, admiring its muscles, throwing tantrums, amazed and scared by the wider world.

It is still wondering what it will be when it grows up, still hoping for greatness. But uncertain of its identify, asking itself profound questions about the way it is changing.

Image copyright AP Image caption Will the rise of countries like Brazil (left) and China dent the US' standing?

Is it a melting pot of immigrants from many lands, some unwilling, where Korean and black and Hispanic culture is celebrated every bit as an English or German heritage?

Or should newcomers, bring no more than a few folk songs from their old home, and squeeze into a white Anglo-Saxon Protestant definition of what it is to be American?

Should America lead the world, from the front, not frightened to right perceived wrongs all over the globe? Or should it, as President Obama wants, be cautious in the exercise of power, sensitive to the feelings of others, willing the right thing, not demanding it?

Then there is the time scale.

Decline can be a long time coming and soft power can echo down the centuries. But often greatness does not endure.

We have all but forgotten the Medes. Carthage is unmourned. And who has heard of the Aksum empire?

But then there is Rome.

By around 40 AD a canny Roman might have predicted the Empire's decline. But it took another 400 years to fall, and it was more than another 1,000 years beyond that before another empire grew as mighty.

In 2,000 years could English be a dead language, used only in liturgy, but still studied in schools? More importantly will American values, often honoured in the breach nowadays, have transformed the world into a place where democracy and freedom of speech are unquestioned values?

Then America would have been mighty indeed.