If chicken has been refrigerated, let stand at room temperature about 15 minutes before preparing salad.
Cook bacon in large skillet over medium heat until well browned and crisp, 4 to 6 minutes. Drain on paper toweling. Reserve fat in skillet.
Place chicken in medium-size bowl. Add red pepper and mushrooms. Crumble in bacon; toss.
Wash romaine lettuce; dry; break into bite-size pieces. Toss in large bowl with green onion.
Cook garlic and white onion in hot bacon fat in skillet until slightly softened, about 5 minutes. Add cider vinegar, Worcestershire sauce, hot sauce and sugar. Bring to a boil. Add salt and pepper, whisking to blend.
Pour three-quarters of hot dressing over chicken mixture; toss to coat. Pour remainder of dressing over greens; toss. Arrange chicken over greens and serve immediately.