Place potatoes into a pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 20 minutes. Drain and slice potatoes into 1/4-inch rounds.
Preheat oven to 400 degrees F (200 degrees C). Spray a large baking sheet with cooking spray.
Unroll the refrigerated pizza crust and spread it out in the baking sheet to fit to the edges. Brush the crust with about 1 tablespoon olive oil.
Bake in the preheated oven until lightly golden and slightly set, about 7 minutes.
Arrange pepperoni slices on a paper towel-lined, microwave-safe plate. Microwave pepperoni on high until heated through, about 30 seconds.
Spread Alfredo sauce over the baked crust; top with Italian cheese blend. Arrange potato rounds in the top left corner of the pizza, forming the blue portion of the flag. Brush potatoes with remaining olive oil. Place mozzarella ball halves on top of the potatoes to resemble the stars of the flag. Arrange pepperoni slices, slightly overlapping, in rows across the pizza to resemble the stripes on the flag.
Bake pizza in the oven until the crust is golden brown and cheese is melted, about 10 minutes.