Mix broth, soy sauce, cornstarch, sugar, garlic powder, ginger and crushed red pepper in small bowl until smooth. Set aside.
Heat oil in large nonstick skillet on medium-high heat. Add chicken in several batches; stir fry 5 minutes until cooked through. Remove from skillet. Repeat with remaining chicken, adding additional oil if needed. Add vegetables to skillet; stir fry 3 minutes. Return chicken to skillet.
Stir soy sauce mixture. Add to skillet; stirring constantly, bring to boil on medium heat and boil 1 minute or until sauce is slightly thickened. Serve with cooked rice, if desired.