The human rights organisation made its criticism on Wednesday in a report to the UN Committee Against Torture, which will start meeting in Geneva this week to consider American compliance with the UN Convention Against Torture and other cruel forms of punishment.
"Evidence continues to emerge of widespread torture and other cruel, inhuman or degrading treatment of detainees held in US custody in Afghanistan, Guantanamo Bay, Cuba, Iraq and other locations," the report said.
The report alleged that no senior American officials have been held accountable for incidents of torture or ill-treatment and said legislation passed by Congress in 2005 has "serious limitations".
One section of that law, it said, refers to "cruel, unusual and inhumane treatment" banned under the US constitution as defined by a series of reservations the US has expressed regarding the UN Convention Against Torture.
The law is a step forward but still could mean the US can employ a narrower interpretation of what constitutes such treatment than is recognised under the convention, Amnesty said. It said that the US should withdraw its reservations to the convention.
"The US government is not only failing to take steps to eradicate torture. It is actually creating a climate in which torture and other ill-treatment can flourish"
Curt Goering, Amnesty's senior deputy executive director for the US, said: "Although the US government continues to assert its condemnation of torture and ill treatment, these statements contradict what is happening in practice.
"The US government is not only failing to take steps to eradicate torture. It is actually creating a climate in which torture and other ill-treatment can flourish."
Amnesty also expressed concern over domestic US violations of the UN torture convention, including use of excessive force by police and abuses against women prisoners.
In Afghanistan, hundreds of detainees remain in American custody with no recourse to due legal process or human rights protection, Amnesty said.
According to Amnesty, there is no longer an international armed conflict in Afghanistan, nor is there a clear or recognised legal framework governing the actions of US forces there.
In the cases of Afghanistan and Iraq, the United States has reportedly improved its procedures for handling prisoners since the Abu Ghraib scandal. But Amnesty said it continues to receive reports of torture or ill-treatment of detainees by American troops.
Committee Against Torture: http://www.ohchr.org/english/bodies/cat/index.htm