Heat a 12-inch skillet over medium. Add the shredded rotisserie chicken and sprinkle with the ground cumin and dried oregano.
Pour in the red enchilada sauce, chunky salsa, and water. Stir to combine and bring to a gentle simmer for 2–3 minutes until the sauce thickens slightly and the chicken is heated through.
Stir in the tortilla strips until evenly coated with the sauce.
Sprinkle the shredded Mexican blend cheese over the top, then remove the skillet from the heat. Allow the residual heat to melt the cheese, about 1–2 minutes.
Top the skillet with dollops of sour cream and optional guacamole in the center, then scatter the sliced green onions over everything.
Serve immediately, scooping portions onto plates or bowls.