Original: She emmigrated to the U.S. and created her own network television series, The Tracey Ullman Show, from 1987 until 1990, from which The Simpsons was spun off in 1989.
Simplified: She emigrated to the U.S. and ended up having her own network television series, The Tracey Ullman Show, from which The Simpsons was spun off in 1989.