Counterpoint: American "cheese" is a crime against food and white bread is rather bland and mushy. Using different breads for firmer textures may not be necessary, but I will definitely stand by people wanting to use more flavorful and better-textured cheeses like mozzarella, provolone, cheddar, or gruyere.
I definitely agree and do those (or a blend) sometimes with a firmer bread or make tiny sandwiches with sliced baguette bread.
But the comfort food kind of grilled cheese is really simple and basic, the kind you can dip in a bowl of Campbell's tomato soup. Kraft, generic (so long as it is not a really bad store brand or completely not cheese at all), Velveeta, and one of my favorites as a kid was one of the poor kids' families got these giant blocks of government cheese (actual American processed cheese that mainly consisted of whatever was being bought up because of bad government policies resulting in too much cheese being made which was then melted down and recombined into this stuff).
It made great grilled cheese.
People went from calling him names like "bowl cut" and "welfare child" to trying to get invites.
Ronald Reagan took a lot of shit for that government cheese but it was great stuff.
I think people would hate "American cheese" a lot less if they called it something different because it excels at a couple of things, like topping a burger or making grilled cheese, or as one ingredient of macaroni and cheese (it is pretty good at getting less meltable cheeses to cooperate).
I should also note there's a difference between American cheese, which is a processed but actual cheese, and stuff they're not allowed to call cheese at all but have to call something like "cheese food product."