Brown the Beef: Set Instant Pot to sauté mode. Add ground beef and cook for 5-7 minutes, breaking it apart until fully browned. Drain excess fat if necessary.
Season: Add salt, pepper, onion powder, and garlic powder to the beef. Stir to combine.
Add Liquids and Rice: Pour in chicken broth, milk, and tomato soup. Stir well. Add rinsed rice and stir again, ensuring rice is submerged in liquid.
Add Corn: Fold in drained corn, distributing evenly.
Pressure Cook: Turn off sauté function. Secure lid with valve in sealing position. Select pressure cook on high for 10 minutes.
Release Pressure: When timer beeps, allow natural pressure release for 10 minutes, then carefully quick release remaining pressure.
Add Cheese: Open lid and stir mixture gently. Add mozzarella and cheddar cheese, stirring until completely melted.
Rest and Serve: Let stand for 3-5 minutes before serving.