Americans are generally really fat is why.
For example, with US adults, per CDC, 73.6% of US adults aged 20 and over were overweight, including obesity. 42.5% of adults 20 and over were obese. See CDC stats
That is a lot of Americans. And then remember how a lot of this correlates with dietary habits (we eat like junk), rates of exercise (we don't), and whether your family and friends are overweight or obese. (More likely to be fat if your friends or parents are fat)
And the sad thing is, overweight basically increases your risk of getting sick and dying all across the board. Eg. it's one of the main comorbidities with COVID
Nihilist is pretty on-point w/ the Food companies too. It's a big multi-factor problem.