Pour 1/2 cup chicken broth into the bottom of the Instant Pot.
Place the chicken breasts on top of the broth (use the trivet if you prefer).
Season the chicken evenly with sea salt, cracked pepper, garlic powder, and Italian seasoning.
Close the lid and set the vent to sealing. Pressure cook on High for 8–10 minutes for thawed chicken or 11–12 minutes for frozen chicken.
When the cook time ends, perform a quick release. Open the lid and check that the chicken's internal temperature is 165°F; if not, cook a few more minutes as needed.
Use two forks to shred or pull the chicken into bite-sized pieces in the Instant Pot.
Switch the Instant Pot to Sauté. Add the cubed cream cheese, grated Parmesan, and chopped spinach; stir until the cream cheese melts and the sauce is smooth and thickened.
If the sauce is too thick, add additional chicken broth (up to the remaining 1/4 cup or more) to reach the desired consistency.
Serve the creamy Parmesan chicken over pasta or rice, or toss with cooked pasta; top with extra grated Parmesan if desired.