The 32-year-old, who is America's third-highest try scorer of all time, was omitted from his country's Rugby World Cup squad after continuously missing training sessions and concerns about his attitude.
The 63-cap flanker signs from San Diego after previously spending three years in Japan with Suntory Sungoliath and NTT Shining Arcs.
"In the past I've had opportunities to come to Europe but because of where I was in life it didn't seem to be the right place for me," Clever told Falcons' official website. "But now I'm really hungry for it and really excited, and I'm looking forward to the opportunity to play here."
Clever, previously voted 2000–2009 American Player of the Decade, will join up with countryman Eric Fry in the North of England.