Place chicken and salsa in a slow cooker; add garlic powder, cumin, chili powder, salt and pepper; stir to combine.
Cover and cook on LOW for 6 to 8 hours. About halfway through cooking time, remove chicken from slow cooker to a cutting board and shred with 2 forks; return to slow cooker and blend with juices.
About 30 minutes before serving, stir corn and beans into chicken mixture; cook for 30 minutes.