I had no idea that plain Doritos were a thing until right now, lol. Plain tortilla chips like Tostitos are very common in the US, though.
Anyway, yeah, a lot of Americans eat shitty and cheap junk food, fast food, convenience food, and processed food. Thank god for small favors that most people (obviously) don't eat anywhere the volume of food that C and J do. (Also, most normal people wouldn't buy something like a huge bag of peanut M&Ms and eat it all by themselves at home. They'd more likely buy it for a party or maybe to put in a candy jar at work. I feel the need to emphasize that C and J are freakish, even if the US is full of fatties.)
And just for fun, here's one of the worst US junk food abominations I've seen in a while; the color is obscene:
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