I thought I asked for a link on this state by state thing. Since it is handled totally by the federal system, I find it interesting.
Desert Fox provided one above. States clearly lying to a FBI guy can get 5 years.
It's important to look at the US-Italy extradition treaty itself, and US practice.
1. The treaty specifies that to be an extraditable offense, the alleged crime must be punishable under the laws of both countries by a prison sentence of more than one year. {This is called "dual criminality".} If the person has already been sentenced, the term remaining of the sentence must be at least six months. (Article 2)
2. Extradition shall not be granted when the prosecution or the enforcement of the penalty shall have become barred by lapse of time {statute of limitations} under the law of the requesting party {Italy in this case}. (Article 8)
3. The request for extradition shall include, for a convicted person, a copy of the judgment of conviction. (Article 10, paragraph 4(a))
4. If the person sought has been convicted in absentia or contumacy, all issues of this aspect of the request {the information to be supplied} shall be decided by the Executive Authority of the US {for a sought person in the US}, and the request for extradition shall include all information relating to the facts of the case. (Article 10, paragraph 5)
5. The requested party {US in this case} shall provide reasons for any partial or complete rejection of the request for extradition. (Article 13, paragraph 2)
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US practice is to examine whether the alleged extraditable offense constitutes a felony under: (a) federal law; (b) state law of the state in which the extradition proceeding is pending {that is, where the sought individual is residing or present}; or (c) the laws of a preponderance of the states. (How dual criminality is determined. Source: Defending the international extradition case. J. Semmelman and K. Snell,
www.nacdl.org; behind a paywall but free view may be available by google searching)
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This is different than what I had claimed earlier, but I believe in practice that the legal effect is the same in this case.
It is important to compare the claimed Italian offense, in sufficient detail, to the US offense. In this case, the Italian offense is (as currently charged) aggravated continuing calunnia. The specific allegations are that a person is charged with falsely claiming in court testimony that she was abused by police during an interrogation, that she made the allegedly false statement to cover-up another crime of calunnia, and that she repeated the allegedly false statement through her lawyers writing appeals including those statements to each of several courts.
The Minerly case of someone pleading guilty to lying to the FBI about police brutality is interesting but somehow doesn't seem to match the Knox case, where the statements are made to a court, as testimony in a court case. Therefore, 18 USC 1001 does not match the Italian situation, because of paragraph (b) of that statute.
That Amanda Knox has lodged a claim with the ECHR against Italy for her conviction for calunnia against Lumumba, that she has been acquitted of the murder/rape of Meredith Kercher, would all play a role in any potential extradition response by the US, I believe.
ETA: A closer federal crime would be perjury, 18 USC 1621, punishable by not more than 5 years imprisonment:
(1) having taken an oath before a competent tribunal, officer, or person, in any case in which a law of the United States authorizes an oath to be administered, that he will testify, declare, depose, or certify truly, or that any written testimony, declaration, deposition, or certificate by him subscribed, is true, willfully and contrary to such oath states or subscribes any material matter which he does not believe to be true; ....
Note that because Knox wrote in her Memoriale 1 of Nov. 6, 2007 that the police had abused her, it would seem that she did believe her statement in court was true, so a review by the US executive would question any conviction for calunnia or perjury.