Adding American cheese to your pasta can help hard cheeses melt effectively. Hard cheeses like parmesan and cheddar struggle to melt due to their low moisture content and unique protein structure. American cheese, which contains emulsifiers, can help achieve a luscious and creamy texture. To use this technique, combine desired cheeses into a sauce, melt them, and then add them to the pasta. This method allows different cheeses to fully incorporate in the sauce. Experiment with various cheese combinations to create unique and flavorful pasta dishes.