Heat oven to 375°F Combine chicken, chili powder and cumin in 10-inch skillet; stir in beans. Cook over medium-high heat, stirring occasionally, until mixture is heated through (2 to 3 minutes). Remove from heat; stir in 1/2 cup sour cream.
To assemble each enchilada, spread 1 tablespoon enchilada sauce on tortilla. Place 1/2 cup bean mixture in center of tortilla; sprinkle with 1 tablespoon cheese. Roll up tortilla; place into greased 13x9-inch baking dish, seam-side down. Repeat with remaining tortillas. Pour remaining enchilada sauce over enchiladas. Cover with aluminum foil.
Bake for 15 minutes or until heated through. Uncover; sprinkle with remaining cheese. Continue baking, uncovered, for 3 to 5 minutes or until cheese is melted.
To serve, top each enchilada with dollop of remaining sour cream; sprinkle with green onions. Serve with chopped tomato and shredded lettuce, if desired.