Mohamed Soltan was charged with destabilising the country in the government crackdown against the outlawed Muslim Brotherhood in August 2013.
The 27-year-old, whose father is a leading Brotherhood official, was arrested in August 2013 and sentenced to life in prison for his role in the so called "Rabaa Operations Room" case.
He had been on a 489-day hunger strike since January 2014, causing relatives to fear for his life. His family say all
charges against him were fabricated.
|Soltan was released from jail on condition he renounced his Egyptian nationality.|
Hundreds of Morsi supporters have died since then. Thousands have been imprisoned, and dozens have been sentenced to death in mass trials described by the UN as "unprecedented in recent history".
Soltan's father, Salah was sentenced to death in the same trial as his son.
President Abdel Fattah al-Sisi passed a law last year allowing foreign nationals convicted of crimes in Egypt to be deported to serve their sentences or be retried in their own countries.
Soltan was released from jail in line with a presidential decree but on condition he renounced his Egyptian nationality.
Soltan's lawyer Halim Hanish told al-Araby al-Jadeed that Soltan was pressed to renounce his Egyptian nationality.
The Egyptian state news agency MENA quoted the state prosecutor as saying Soltan would serve the rest of his sentence in the US, in line with the decree allowing him to leave Egypt.
Soltan's brother Omar, who lives in the US, wrote on Facebook: "The US government has exerted much effort [and] managed to ensure Mohamed's safe return."
Tears, hugs and cries of "welcome home" greeted Soltan as he arrived in Washington on Monday. Soltan got out of his wheelchair on arrival and kissed the ground.
Egyptian-Canadian al-Jazeera journalist Mohamed Fahmy also gave up his Egyptian citizenship in the hope the Egyptian government would deport him. Fahmy however has not been deported and he continues to stand retrial.
Another dual-nation citizen currently in prison is Egyptian-Irish teenager Ibrahim Halawa, who has been held for almost two years after being arrested at a Muslim brotherhood protest in August 2013.