The US foreign service, to judge by the leaked cables, seems a resource which is over-bureaucratised and under-used.
A year in which Uncle Sam's stumbling came into full view
For once the experts can agree on the key trend of the past year. It is the decline of the US, as power seeps away towards the rising nations of the south and east, principally China, India and Brazil.
The deflation of the world's only superpower is cogently described by the doyen of British historians, Eric Hobsbawm. "For the past 500 years the centre of the world's dynamism, wealth and power was Europe, and then it extended to North America. That is where it stayed until the late 20th century.
"One thousand years ago civilisation was all in the south and east, and the west was a provincial, backward place. The world's centre of gravity, economically and possibly politically, is shifting back again."
The US, according to Prof Hobsbawm, is no longer "the big gorilla". It cannot make things happen, and cannot stop things from happening. The release of US diplomatic cables by WikiLeaks, he adds darkly, is "an archive of imperial retreat".
The professor is well known for his Marxist leanings, so the hint of gloating in his analysis is no surprise. The story of America's relative decline, whether greeted with joy or foreboding, is the universal narrative of 2010. But how seriously should we take it?
The past year provided plenty of examples of the stumbling giant. President Barack Obama failed to make good his promise to rein in Israeli settlement building. Next year, the US will withdraw from Iraq, shutting the door on a costly military failure. In Afghanistan, with enormous effort, the US military has just managed to halt the momentum of the Taliban, but the path to a political settlement is still barred. The limits of US power are more evident than ever.
To some extent this has always been true. America could not prevent the communist takeover in China in 1949, or unseat Fidel Castro in Cuba despite 50 years of trying, or keep the Shah of Iran in power. America has been written off many times: after its defeat in Vietnam in 1975, or when the future seemed to belong to Japan in the 1980s.
It should be remembered that US power has relied on extraordinary strokes of luck. In 1945, at the end of the Second World War, the US found itself almost unscathed while the rest of the industrialised world was in ruins, allowing it to dominate the global economy for a generation. In the 1980s, the Soviet Union, outspent in the arms race by America, gave up its pretensions to a superpower role and fell apart.
This was America's "unipolar moment", the title of a 1990 article by the right-wing commentator Charles Krauthammer, which highlighted an extraordinary development. The world suddenly had only one pole of power, not many, as has often been the case in history, or just two, as had prevailed during the Cold War.
American optimism has tended to blank the key word "moment" from the phrase, and see its global hegemony as a continuum. The original article said no such thing: in a generation or so, Krauthammer predicted, there would be great powers "co-equal" with the United States.
That time is approaching. No country can compete with the 560 military bases that the US keeps abroad, nor match its defence spending, almost as much as the rest of the world put together. Yet already China is pushing back at the US naval presence close to its shores and its protection of Taiwan, Japan and other Washington allies.
The US is not going to fade away overnight. Just as the effectiveness of its military power has been exaggerated and the possibility of its unchallenged empire left unquestioned, so its decline will not be so brutal as some predict.
Power in the future will be exercised regionally. There will be an Asian bloc, where China and India will be the local powers, as they were in the days when Europe was stuck in the Dark Age. Europe will live in some kind of partnership with Russia. The Middle East region will have to look after itself, with the surrounding powers eyeing its resources.
The US will dominate the Americas, but it will not be confined to the western hemisphere. It will look both ways - to the east, towards nations with cultural affinity and the source of some of its oil, and to the west, the booming markets of Asia.
In this respect, the US of the future has been compared to the Byzantine Empire. In decline for centuries, it hung on until 1453 - not due to its military prowess but thanks to subtle diplomacy. It also looked both east and west.
Clearly the US cannot afford its vast military expenditure, and where it leaves a vacuum, others will move in. It will need to develop a new type of diplomacy less focused on the projection of military power. We can already see the US engaging with Iraqi domestic politics and in the complex diplomacy of tightening sanctions against Iran.
The military, and the barons of the security industry complex which have prospered in the war on terror, are still in charge in Washington. The generals can be subtle, as shown by David Petraeus, the commander of international forces in Afghanistan. But the US foreign service, to judge by the leaked cables, seems a resource which is over-bureaucratised and under-used.
In the past, America has enjoyed the luxury of domestic politics trumping the national interest, as exemplified in unconditional support for Israel. This is a large dose of sentiment in this relationship and, as Gen Petraeus dared to say this year, "the perception of US favouritism of Israel" is harming US interests. Harsher times will require a more rigorous alignment of foreign policy with national interest.
As for the people of the Middle East, the leaked US cables have shown that the presence of the American gorilla on the ground has led to a certain passivity among the Arab states, made worse by succession issues in some of the leading players. With the gorilla's footprint lessening, it will be time for the Arab states to come into their own.