Place a 12-inch skillet over medium heat and add the shredded rotisserie chicken.
Season the chicken with the ground cumin and dried oregano, stirring to distribute evenly.
Pour in the red enchilada sauce, chunky salsa, and water; stir to combine and bring to a simmer.
Simmer the mixture for 2–3 minutes until the sauce thickens slightly and the chicken is heated through.
Stir in the tortilla strips until they are coated with sauce, then sprinkle the shredded Mexican blend cheese evenly over the top.
Remove the skillet from the heat and let sit a minute for the cheese to melt.
Top the skillet with dollops of sour cream, add guacamole if desired, and sprinkle with sliced green onions; serve immediately.