a lot of your food is just really unhealthy. I know from the keto subs that many basic ingredients have added sugar for no good reason, and that’s not even going into that whole HFC thing.

That is true. It is possible to eat only healthy options if you make a concerted effort to, but if you casually just eat what's convenient, or eat at restaurants, you will be consuming astronomical portions and really wacky macro ratios.

People in the USA make the "well unhealthy food is cheap" argument which is only partially true; the more accurate claim is "convenient food is unhealthy". I spend significantly less money on healthy ingredients and make my own food than someone who is buying convenient microwavable and prepared meals; but, it takes me a decent amount of time each day to cook versus a minute watching a microwave. I think cultural aspects of being overworked sneak in to this situation as well: when you have so little free time, and have worn yourself out at work, unless you really enjoy the act of cooking, you are likely to just reach for convenience rather than putting in effort to cook something healthy. Then, you have the interaction of eating unhealthy foods to self-soothe as a method of coping with the reality of being overworked.

There are a lot of moving pieces but, all else being equal (that is, the population eats the same things and keeps the same activity level): the healthcare system in the USA could have a lot less waste and overhead (read: siphoned profits) and thus be a lot less costly to interact with.