Spray the inside of a 4 to 6-quart crock pot with non-stick cooking spray.
Place the cut chicken pieces into the bottom of the crock pot.
In a medium bowl, mix together the condensed cream of chicken soup, sour cream, shredded cheddar cheese, chopped onion, chopped green bell pepper, garlic powder, black pepper, and salt until well combined.
Pour the soup mixture evenly over the chicken in the crock pot and stir gently to combine.
Cover and cook on low for 3 hours, or until the chicken is cooked through and tender.
After 3 hours, evenly spread the frozen tater tots over the top of the chicken mixture in the crock pot.
Sprinkle the shredded mozzarella cheese evenly over the tater tots.
Cover and cook on low for an additional 1 hour, or until the tater tots are cooked through and the cheese is melted and bubbly.
Carefully serve the casserole hot directly from the crock pot.