Add the chicken breasts, diced potatoes, chicken broth, buffalo wing sauce, celery, carrots, garlic powder, salt, and black pepper to the slow cooker. Stir gently to combine.
Cover and cook on low for 6 hours or until the chicken reaches an internal temperature of 165°F and the potatoes are fork-tender.
Remove the chicken breasts and shred them with two forks, then return the shredded chicken to the slow cooker.
Add the cubed cream cheese and stir until it melts completely into the soup, creating a creamy consistency.
Ladle the soup into bowls and top each serving with crumbled blue cheese and sliced green onions.