Davies, 23, underwent several hours of surgery after sustaining a lacerated bladder and fractures to his tibia and femur bones in his right leg, the U.S. Soccer Federation said in a statement.
A person in the car with Davies was killed in the accident, federation spokesman Neil Buethe said in the statement.
Davies's injuries were not considered life-threatening, but would rule him out of playing the 2010 World Cup in South Africa.
"Injuries of this nature usually require a recovery period of six to 12 months and extensive rehabilitation," U.S. Soccer physician Dan Kalbac told reporters.
"Due to Charlie's fitness level, his prognosis recovery and his ability to resume high-level competition is substantially improved."
"As a team we were saddened to learn this news," U.S. coach Bob Bradley said. "Our thoughts and prayers go out to Charlie and Charlie's family as well as the people in the car and the families of the others involved."
