Whisk together rice vinegar, oil, sugar, salt, and garlic powder in a medium saucepan over medium. Bring to a boil, stirring constantly. Remove from heat; cool 20 minutes.

Combine black beans, black-eyed peas, corn, bell peppers, jalapeños, onion, and scallions in a large bowl. Pour dressing over bean mixture, and toss to combine. Refrigerate 4 hours before serving. Serve with tortilla chips.