premise: British Prime Minister Tony Blair has failed to influence United States President George W Bush's foreign policy, a top foreign affairs think-tank said Tuesday.
  A briefing paper from Chatham House also said that the "terrible mistake" of the 2003 Iraq invasion, led by the United States but strongly backed by Britain, would resonate long after Blair leaves office next year.
  "The root failure of Tony Blair's foreign policy has been its inability to influence the Bush administration in any significant way despite the sacrifice -- military, political and financial -- that the United Kingdom has made," said the paper, penned by outgoing director Victor Bulmer-Thomas.
  He added that Iraq was a foreign policy "watershed" which, like the 1956 Suez crisis, would alter the relationship with the United States for many years to come.
  "The post 9/11 decision to invade Iraq was a terrible mistake and the current debacle will have policy repercussions for many years to come," the paper added.
   What caused the relationship with the United States to be altered?
hypothesis: the 2003 Iraq invasion