According to Owen Barder: ("Why the US-UK extradition treaty should not be ratifiedr"), the US-UK extradition treaty seems to be facing significant opposition to its ratification in the United States Senate.
The US Senate is choking on the US-UK Extradition Treaty (full text pdf) because they are concerned that it might adversely affect civil liberties of people living in the United States. The irony is that the treaty protects those liberties much better than it protects the liberties of British citizens. But we have no Senate to protect us.[...]
The proposed extradition treaty was signed on March 31, 2003 by US Attorney General, John Ashcroft, and the British Home Secretary David Blunkett. It was transmitted by the President to the U.S. Senate Committee on Foreign Relations in April 2004, and was considered by them on 15 November 2005. The Committee hearings were held in private and no transcript has been published, so we don’t know exactly what happened, but it appears that the Committee declined to vote on the treaty. This is a major problem for the passage of the treaty, as the the full Senate cannot consider the treaty until the Committee has approved it.
Opposition to the treaty in the US is based on fears that it removes the exception for political offences, allows for extradition even if no US law has been broken, removes any statute of limitations, applies retroactively, and allows the UK authorities to try a person for an offence other than that for which he or she was originally extradited. The failure of the Committee on Foreign Relations to vote on the treaty is the result of opposition from American Civil Liberties Union (which probably doesn’t matter the Republican-controlled Senate) and from the Ancient Order of Hibernians and other Irish-American organisations (which probably does matter).