The G20 became the G19 as it ended. On the Paris climate accords the United States was left isolated and friendless.

It is, apparently, where this US President wants to be as he seeks to turn his nation inward.

Donald Trump has a particular, and limited, skill-set. He has correctly identified an illness at the heart of the Western democracy. But he has no cure for it and seems to just want to exploit it.

He is a character drawn from America's wild west, a travelling medicine showman selling moonshine remedies that will kill the patient.

And this week he underlined he has neither the desire nor the capacity to lead the world.

Given the US was always going to be one out on climate change, a deft American President would have found an issue around which he could rally most of the leaders.

He had the perfect vehicle — North Korea's missile tests.

So, where was the G20 statement condemning North Korea? That would have put pressure on China and Russia? Other leaders expected it and they were prepared to back it but it never came.

There is a tendency among some hopeful souls to confuse the speeches written for Mr Trump with the thoughts of the man himself.

Sorry, this video has expired Trump 'has no desire and no capacity to lead the world', Chris Uhlmann says

He did make some interesting, scripted, observations in Poland about defending the values of the West.

And Mr Trump is in a unique position — he is the one man who has the power to do something about it.

But it is the unscripted Mr Trump that is real. A man who barks out bile in 140 characters, who wastes his precious days as President at war with the West's institutions — like the judiciary, independent government agencies and the free press.

He was an uneasy, awkward figure at this gathering and you got the strong sense some other leaders were trying to find the best way to work around him.

There is a divide between the scripted Mr Trump, and the one who speaks off-the-cuff. ( AP: Ryan Remiorz )

Mr Trump is a man who craves power because it burnishes his celebrity. To be constantly talking and talked about is all that really matters. And there is no value placed on the meaning of words. So what is said one day can be discarded the next.

So, what did we learn this week?

We learned Mr Trump has pressed fast forward on the decline of the US as a global leader. He managed to diminish his nation and to confuse and alienate his allies.

He will cede that power to China and Russia — two authoritarian states that will forge a very different set of rules for the 21st century.

Some will cheer the decline of America, but I think we'll miss it when it is gone.

And that is the biggest threat to the values of the West which he claims to hold so dear.