Archbishop of Canterbury Dr Rowan Williams has launched a stinging attack on US policy, comparing it unfavourably with the British Empire.
Dr Williams says Western modernity 'eats away at the soul'.
In a magazine interview, he said the British Empire had "rightly or wrongly" poured energy and resources into administering lands it had taken over.
But he told Muslim lifestyle glossy Emel the US had assumed all Iraq needed was a "quick burst of violent action".
US officials said billions of dollars had been spent helping Iraqi people.
Moral high ground
Dr Williams said the US, as the only "global hegemonic power", was trying to accumulate influence and control, rather than territory. But he said: "That is not working," describing the result as "the worst of all worlds".
He told the magazine the US had lost the moral high ground since the 11 September attacks and needed to take steps including "generous aid" to "the societies that have been ravaged", a "check on the economic exploitation of defeated territories" and a "demilitarisation" of its presence in them in order to recover.
The US believed that in Iraq it could then leave others to "put it back together", he said.
Of Britain's role in the conflict, Dr Williams - a long-term critic of the invasion - said: "A lot of the pressure around the war in Iraq was, 'We've got to do something! Then we'll feel better.' That's very dangerous."
He described violence as "a quick discharge of frustration", saying "It serves you. It does not serve the situation.
"Whenever people turn to violence what they do is temporarily release themselves from some kind of problem but they help no-one else."
Dr Williams raised questions about the modern Western definition of humanity, saying: "There is something about Western modernity which really does eat away at the soul."
He warned the fast pace of modern life could "get in the way of the soul".
He told the magazine: "The worst message we can give off is compulsive anxiety, 'I've got to fix everything'."
But, in a statement, the US Embassy in London rejected the archbishop's claims that the US did not help rebuild countries with extra resources.
It said the US was "the largest donor of aid of any country in the world" and that "billions of dollars of financial, technical, and medical assistance" had been given to the people of Iraq.
"In addition, President Bush has doubled US overseas development assistance and almost tripled our aid to Africa," the statement continued.
"We have given $15 billion (£7.3 billion) over the last five years to prevent and treat HIV/Aids in Sub-Saharan Africa and the Caribbean."
It added that the US was also the "largest single donor to the welfare of Palestinian refugees".