Preheat oven to 400 degrees F (200 degrees C). Spray a skillet with cooking spray.
Cook and stir beef sirloin in the prepared skillet over medium heat until browned on the outside and slightly pink in the middle, 3 to 4 minutes. Transfer sirloin to a plate.
Spray the skillet with butter-flavored cooking spray. Add mushrooms, onion, and green bell pepper; cook and stir until just turning tender, about 5 minutes.
Roll pizza dough onto a baking sheet and top with American cheese. Spoon mushroom mixture and sirloin over American cheese layer and top with Mexican cheese blend.
Bake in the preheated oven until cheese is golden brown, 15 to 20 minutes.
