Preheat the oven to 350 F.
Place the cooked macaroni into a large bowl.
In a small bowl, combine the seasoning salt, pepper, garlic powder and onion powder. Sprinkle half of this seasoning mixture and 1 cup of shredded sharp cheddar over the macaroni and toss to combine.
In large saucepan over medium-high heat, melt the butter. Whisk in the flour, working continuously until it makes a light roux.
Reduce the heat to medium and continue whisking as you slowly add the milk. Once all the milk is incorporated, cook 5 to 8 minutes, or until ingredients begin to simmer.
Add the cream cheese and diced American cheese in batches, and stir to melt and blend. Add 1½ cups of the shredded cheddar and turn off the heat.
Season the cheese sauce with the remaining seasoning mixture and stir well. Add the eggs and continue to stir to combine.
Spread the macaroni evenly into a cast iron skillet.
Pour the cheese sauce over the noodles, making sure to cover them well. Fold in the chopped bacon. Top with the remaining cup of cheddar cheese.
Cover the skillet with foil and bake for 30 minutes, or until the cheese is bubbling around the edges.