Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
In a medium saucepan, combine tomatoes with chiles, chicken broth, flour, cumin and garlic powder. Bring to a boil over medium heat; reduce heat and simmer 5 minutes. Add cream cheese and stir until melted.
Mix together chicken, onion and 1/4 cup of the sauce in a large bowl. Fill each tortilla with about 1/3 cup of the chicken mixture and roll up. Place in prepared baking dish.
Pour remaining sauce over enchiladas. Sprinkle with Monterey Jack cheese.
Bake in preheated oven for 25 minutes or until cheese is melted and bubbly.