Set the Instant Pot to Sauté and heat the olive oil until shimmering.
Add the diced onion and cook, stirring frequently, until softened (about 3–4 minutes).
Stir in the salsa, ground cumin, chili powder, garlic powder, salt, black pepper, and chicken broth until combined.
Place the chicken breasts into the pot, partially submerging them in the liquid, then close the lid and set the valve to sealing.
Cook on high pressure for 10 minutes, then allow a natural pressure release for 5 minutes before doing a quick release for any remaining pressure.
Open the lid, remove the chicken to a cutting board or bowl, shred with two forks, and return the shredded chicken to the pot; toss in the cooking juices to coat.
Serve the shredded chicken in tortillas or bowls with desired toppings (recipe yields about 8 tacos).