I attended my first Cambridge Festival in 1975 ( went again in 1976 ), and I have to say that the acts which remain in my memory were almost all American.
David Bromberg (along with Dick Fegy) , Paul Geremiah, Country Gazette, Leo Kottke, the David Grisman Band (with Tony Rice David Grisman and Bill Keith) , Don McLean, Isaac Guillory, Stephen Wade, and others whom I would recall given time.
Emmylou is simply carrying on the tradition of outstanding American artists at Cambridge.