Prepare the chicken by cutting the breasts into 1–2 inch pieces and rinse the rice until the water runs clear.
Add the cubed chicken, drained black beans, frozen corn, salsa, chicken broth, and taco seasoning to the Instant Pot and stir to combine.
Add the rinsed rice on top of the other ingredients without stirring.
Secure the Instant Pot lid, set the valve to sealing, and cook on high pressure for 10 minutes.
When cooking is complete, carefully perform a quick release of the pressure and remove the lid following the manufacturer's instructions.
Stir everything gently to combine; the chicken should be tender. Sprinkle the shredded Mexican cheese over the top and replace the lid for a few minutes to allow the cheese to melt.
Serve the mixture in bowls and top with diced avocado, sour cream, and cilantro as desired.