Preheat an oven to 350 degrees F (175 degrees C). Grease a 9×13 inch baking dish.
Slice potatoes with skins on into 1/4 inch thick slices. Place the potatoes into a large pot and cover with salted water. Bring to a boil over high heat, then reduce heat to medium-low, cover, and simmer until tender, 10 to 15 minutes. Drain and allow to steam dry for a minute or two.
Mix together the mayonnaise, sour cream, onion and garlic powders, seasoned salt, pepper, bacon, onion, and American cheese in a bowl. Stir in the potato slices. Pour mixture into prepared baking dish. Sprinkle top with grated Parmesan cheese.
Bake until bubbly and beginning to brown, 35 to 40 minutes.