A single slice of American cheese weighs 28 grams. Approximately 7 grams of that slice is fat, 5.5 grams is protein and 2 grams is carbohydrate, the U.S. Department of Agriculture reports. The rest consists of other nutrients and water. According to the USDA, a single slice of American cheese contains 95 calories. Fats provide around 72 of those calories within the serving, while proteins deliver 15 calories and carbohydrates offer 8 calories.