Complex sentence: Smash Hits were one of the few publications supportive of his music; the American press, who were considered his biggest supporters, praised Numan's work on "I, Assassin".
Split into simpler sentences: Smash Hits were one of the few who were supportive of his music. The American press, who were considered his biggest supporters, praised Numan's work on what he produced on "I, Assassin".