Who was the first American to go outside an orbiting spacecraft attached only by a tether?

During the Gemini IV mission in June 1965, which was the second manned space flight in NASA's Project Gemini, the highlight of the mission was the first spacewalk by an American. Astronaut Edward "Ed" H. White floated free outside the U.S. spacecraft; he was tethered to the craft for approximately 20 minutes.

About three months after Soviet Cosmonaut, Aleksei Leonov, U.S. Astronaut Ed White became the second person and first American to walk in space. He was able to do this while his teammate James McDivitt photographed him through the hatch window. It was reported that White enjoyed his spacewalk so thoroughly he had to be told several times to return to his spacecraft. He spent nearly twice as long as he was originally scheduled on his spacewalk.