Put the bacon in a large nonstick saute pan over medium heat. Cook just until the fat is rendered out, 5 to 7 minutes. (The bacon should not brown at all.) Remove the bacon from the pan and place in the bowl of a small food processor. There should be about 2 tablespoons of bacon fat that has collected in the pan.
Place the buns into the warm bacon fat, cut-side down. Toast the buns they are until golden brown around the edges, about 2 minutes. Set aside for burger assembly.
Pulse the par-cooked bacon in the food processor until it is coarsely ground, 30 seconds to 1 minute. Transfer the bacon to a large mixing bowl. Add the ground beef, Worcestershire sauce, 1/2 teaspoon salt and 1/2 teaspoon pepper. Use your hand to gently work the bacon and seasonings into the ground beef. Divide the meat into 4 portions (6 to 7 ounces each). Loosely pack the meat into 4 thick patties, using your thumb to create a shallow dimple in the center of each. Sprinkle the outside of each patty with salt and pepper as desired.
Preheat the grill and generously oil the grill grates. Place the patties on the grill and cook to the desired degree of doneness, 3 to 5 minutes on each side. Top each patty with a slice of American cheese and cover the grill to allow the cheese to melt, 30 seconds.
Assemble the burgers and top with ranch, lettuce, tomato slices and red onion. Serve immediately.