Make the dressing: In a small bowl, whisk together ranch dressing and taco seasoning until well combined. Cover and refrigerate until ready to use.
Cook the chicken: Season chicken pieces with salt and pepper. Heat a large non-stick skillet over medium-high heat. Cook chicken, stirring occasionally, until cooked through and lightly golden, about 12 minutes.
Assemble the salad: In a large bowl, combine chopped romaine lettuce, diced tomatoes, corn kernels, sliced green onions, black beans, shredded cheese, and cilantro.
Add chicken and dressing: Let chicken cool for 5 minutes, then add to the salad along with lime juice. Pour dressing over the salad a little at a time and toss gently until everything is evenly coated.
Serve immediately: Top with crushed tortilla chips and serve in individual bowls. Add extra dressing on the side if desired.