Bring water to a boil in a medium saucepan; stir in couscous. Remove from heat; cover and let stand 5 minutes. Fluff with a fork. Combine couscous, green onions, bell pepper, mint, shrimp, and green peas in a bowl; set aside.
Combine broth and remaining ingredients; stir well with whisk. Pour dressing over couscous mixture, tossing gently to coat.