Place the chicken breasts in the bottom of the crockpot.
Pour the chicken broth over the chicken, then sprinkle the taco seasoning evenly on top.
Add the diced onion, diced tomatoes, and green chiles to the crockpot, stirring gently to combine.
Cover the crockpot and cook on low for 6 hours or high for 3 hours until the chicken is cooked through and can be easily shredded.
Once cooked, carefully remove the chicken from the crockpot and shred it using two forks.
Return the shredded chicken back to the crockpot and mix it with the sauce.
Warm the tortillas in a skillet or microwave, then fill each with a portion of the chicken mixture.
Top with shredded lettuce, diced tomatoes, cheddar cheese, and a dollop of sour cream.
Garnish with chopped cilantro and serve with lime wedges on the side.