Remove any packaging from the chicken. Place the chicken breasts in the Instant Pot insert in a single layer.
Pour the chunky salsa over the chicken, then add the dark balsamic vinegar, chili powder, and ground cumin on top.
Close the Instant Pot lid and set the steam release valve to the sealed position.
Select the Poultry preset and adjust to High pressure using the Adjust button if needed, then set the cook time to 25 minutes.
When cooking completes, let the pressure sit for 5 minutes (natural release), then carefully quick-release any remaining pressure and open the lid.
Use tongs or a slotted spoon to remove the chicken to a cutting board or bowl. Shred the chicken with two forks.
Return the shredded chicken to the Instant Pot and stir to coat it thoroughly in the sauce.
Serve the shredded chicken in corn or whole wheat flour tortillas with your favorite taco toppings.