Preheat the oven to 425 degrees F. Grease a 9x13-inch baking dish with butter.
Make the Bread Crumbs: In a food processor, process the bread until it forms fine crumbs (you should have about 4 cups crumbs). In a large skillet, heat the butter over medium-low heat. When it foams, add the garlic and cook, stirring, until the garlic is fragrant but not browned, 1 to 2 minutes. Add the bread crumbs, increase the heat to medium, and cook, stirring frequently, until toasty and browned, 7 to 9 minutes. Stir in the salt and pepper, remove from the heat, and transfer to a large plate to cool for 5 minutes. Stir in the Parmesan cheese.
Make the Mac and Cheese: In a large pot of salted boiling water, cook the pasta according to the al dente directions on the package (if not included, cook for one minute less than called for). Drain, rinse, and toss with the vegetable oil to prevent sticking.
In a large saucepan or Dutch oven, heat the butter over medium-high heat until melted. Add the flour and cook, constantly whisking, until it turns a light and toasty brown color, 3 to 6 minutes. Gradually add the milk while whisking, then increase the heat to high and bring it to a boil. Reduce the heat to medium and cook, whisking, until it thickens, 4 to 5 minutes. Add the cheeses, a few handfuls at a time, and whisk the sauce until smooth. Whisk in the salt, black pepper, and cayenne. Stir in the cooked pasta, and season to taste with more salt and pepper.
Pour the mixture into the buttered baking dish and spread the bread crumbs evenly over the top. Bake until the topping is browned and crisp and the cheese is bubbling, about 8 minutes to 10 minutes. Leftovers can be stored, covered, in the refrigerator for up to 4 days.
If you cannot get American cheese where you live, a good substitute would be Colby cheese.
The original recipe calls for 3/4 teaspoon or more cayenne pepper, but since I would be serving this to the boys, I just used a small amount. If you like spicy, ramp it up!