Combine sour cream and 2 tablespoons salsa in a small bowl; stir well. Cover and chill until ready to serve.
. Cook beef, onion, and bell pepper in a large nonstick skillet over medium-high heat until browned, stirring to crumble beef. Drain well; return meat mixture to pan. Stir in 1 cup salsa, chili powder, cumin, and salt; bring to a simmer over medium heat, and cook 3 minutes.
. Place 1 cup chips on each of 4 serving plates; top each with 3/4 cup meat mixture, 1/4 cup lettuce, 1/4 cup tomato, 2 tablespoons cheese, and 1 tablespoon jalapeño slices. Drizzle 2 tablespoons sour cream mixture over each serving.