Lightly coat a 5-quart slow cooker with cooking spray. In a large bowl, whisk together melted butter, Worcestershire sauce, seasoned salt, and garlic. Add the chicken and toss until evenly coated, then transfer it to the slow cooker.

Using the same bowl, mix together the diced tomatoes, soup, and chopped chiles. Pour this mixture over the chicken. Cover and cook on High for 2 to 3 hours or Low for 3 to 4 hours, until the chicken reaches an internal temperature of at least 165°F.

Remove the chicken and place it on a cutting board. Let it rest for about 5 minutes until cool enough to handle. Meanwhile, stir the cream cheese and Cheddar cheese into the slow cooker, cover, and cook on High for another 5 to 10 minutes until the cheese is melted and smooth. Stir to combine.

Shred the chicken using two forks, then return it to the slow cooker along with the cooked spaghetti. Stir everything together, then sprinkle with fresh parsley before serving.

To make ahead and freeze: In a large bowl, mix the melted butter, Worcestershire sauce, seasoned salt, and garlic. Toss the chicken in the mixture, then transfer it to a gallon-sized resealable freezer bag. In the same bowl, mix the tomatoes, soup, and chiles, then pour over the chicken. Seal the bag tightly, removing as much air as possible, and lay it flat in the freezer for up to 3 months. When ready to cook, thaw in the refrigerator for 8 to 24 hours, then spray the slow cooker with cooking spray and pour in the thawed mixture. Cook as directed.