Speaking in a live, exclusive interview with Robin Roberts on ABC's Good Morning America Friday morning, Knox said she watched the verdict with her family as it was read live, televised online by an Italian television station.
"This has really hit me like a train," a sometimes tearful Knox told Roberts. "I really did not expect this to happen. I expected so much more," she said, from the Italian justice system.
Knox vowed to fight the conviction "until the very end. It's not right, and it's not fair. I'm going to do everything I can," she said.
In Thursday's ruling, the court increased Knox's sentence to 28½ years in prison, raising the specter of a long extradition fight.
Knox is now facing what seemed like a distant worry when she was giving national television interviews and promoting her autobiography last year: the possibility of being returned to Italy to serve decades in prison for the death of her roommate, Meredith Kercher.
Any decision on whether to extradite the 26-year-old from the U.S. is likely months away, at least. Experts have said it's unlikely that Italy's justice ministry would request Knox's extradition before the verdict is finalized by the country's high court.
If the conviction is upheld, a lengthy extradition process would likely ensue, with the U.S. State Department ultimately deciding whether to turn Knox back over to Italian authorities to finish serving her sentence.
Here's how that might play out.
Extradition is the process of one country surrendering to another country a person who has been accused or convicted of a crime. Under the terms of the extradition treaty between the U.S. and Italy, the offense must be a crime in each country and punishable by more than one year in prison.
Any request to extradite Knox would go to the U.S. State Department, which would evaluate whether Italy has a sufficient case for seeking Knox's return. If so, the State Department would transfer the case to the Justice Department, which would represent the interests of the Italian government in seeking her arrest and transfer in U.S. District Court.
American courts have limited ability to review extradition requests from other countries, but rather ensure the extradition request meets basic legal requirements, said Mary Fan, a former U.S. federal prosecutor who teaches law at the University of Washington in Seattle.
"The U.S. courts don't sit in judgment of another nation's legal system," Fan said.
THE POLITICAL AND THE LEGAL
Fan suggested that any decision by the State Department on whether to return Knox to Italy is "a matter of both law and politics." From an American standpoint, the case at first seems to raise questions about double jeopardy - being tried twice for the same offense, as barred by the U.S. Constitution. Knox was first convicted, then acquitted, then, on Thursday, the initial conviction was reinstated.
Some observers have dismissed the double-jeopardy issue because Knox's acquittal was not finalized by Italy's highest court.
That said, creative defense lawyers might make an effort to fight extradition over concerns about the legal process or the validity of the conviction, Fan said, and those arguments could carry political weight too. "Many Americans are quite astonished by the ups and downs in this case, and it's the U.S. that will ultimately be making the call about whether to extradite," Fan said.
Sen. Maria Cantwell, D-Wash., said in a statement Thursday she was "very concerned and disappointed by this verdict."
"I will continue to closely monitor this case as it moves forward through the Italian legal system," Cantwell said.
Christopher Jenks, a former Army attorney who served as a State Department legal adviser and now teaches at Southern Methodist University's law school, said Italy has a low bar to clear in compiling a legally sufficient extradition request.
"There would be a political or policy decision to be made by the State Department, but it's got to be founded in law or in reason," he said.
Jenks noted that the extradition treaty works both ways.
"If the U.S. ever wants to have any chance of extraditing an Italian murder suspect who has allegedly killed people in the U.S.," he said, "you have to give to get."
HAS ITALY HAD ENOUGH?
There have been other high-profile tussles over whether Americans suspected of crimes in Italy would face justice there.
In 1998, a low- and fast-flying U.S. Marine jet sliced a cable supporting a gondola at a ski resort in the Italian Alps, killing 20 people. Many Italians wanted the pilot and crew tried in Italy, though NATO rules gave jurisdiction to the U.S. military. The pilot faced a court martial in the U.S. and was acquitted of negligent homicide charges.
Italian courts convicted - in absentia - 26 CIA and U.S. government employees in the 2003 kidnapping of an Egyptian cleric suspected of recruiting terrorists in Milan. One, a U.S. Air Force colonel, was pardoned last year on the grounds that it was unprecedented to try an officer of a NATO country for acts committed in Italy. Another, the former CIA base chief in Milan, Robert Seldon Lady, has also requested a pardon. Lady was briefly held last summer in Panama based on an international arrest warrant issued by Italy, which has not yet formally requested his extradition.
"I suspect that the Italians feel there have been enough incidents of them not being able to prosecute Americans for crimes committed in Italy," Jenks wrote in an email.
The Associated Press contributed to this report.