The radical cleric landed in America on Saturday after he was removed from the UK following Friday's failed appeal against extradition at the High Court.
Within hours of landing, the former imam at the Finsbury Park mosque in north London was in a Manhattan courtroom facing terror charges, but he did not enter a plea or make an application for bail in the brief hearing.
Hamza arrived in court without the hook he uses as a hand, and complained through his lawyer that he wanted it to be given back.
He was jailed in the UK for seven years for soliciting to murder and inciting racial hatred in 2006. He first faced an extradition request from the United States in 2004.
He has been charged with 11 counts of criminal conduct related to the taking of 16 hostages in Yemen in 1998, advocating violent jihad in Afghanistan in 2001, and conspiring to establish a jihad training camp in Bly, Oregon, between June 2000 and December 2001.
Four other men – Khaled Al-Fawwaz, Adel Abdul Bary, Syed Ahsan and Babar Ahmad – pled not guilty to other terror charges.
They appeared alongside Hamza in New York.