I watched a documentary called "Fed Up" that addressed this. I haven't verified the accuracy of the documentary, but here was the explanation it gave, which is

I watched a documentary called "Fed Up" that addressed this. I haven't verified the accuracy of the documentary, but here was the explanation it gave, which is consistent with your first sentence. "Fat" was declared the enemy, so highly processed food providers started removing fat. The food tasted bad. So they added in sugar. So now people were eating much more sugar, but still craving fat, and seeking it from other sources. So it became a double whammy. At the same time, as many products (such as dairy) were being made low-fat, the highly processed food industry needed something to do with all that fat, so it launched the "cheese glorious cheese" campaign, where highly processed cheese (with lots of added salt) was now added to almost every conceivable thing, at low cost (because it was left over from the milk). Cheese went into pizza toppings (extra cheese!), pizza crusts, processed mac n cheese, all kinds of approximations of previous foods. So now, Americans, instead of eating fat where it naturally exists, were instead eating lots of low fat processed food products with sugar to replace the fat, and then eating the fat in other products, with lots of added salt. The other thing the documentary asserted (well, a physician in the documentary asserted) is that the popular believe that "a calorie is a calorie regardless of source" is incorrect in terms of how the body processes calories from different food sources. A calorie of sugar can lead to weight gain in a way that a calorie from other sources doesn't. Again, this is just what was in the documentary "fed up", I don't know much more about it than that. Rather than focusing too much on the difference between Europe and the US, I think it might be useful to realize the difference between "big, corporate food" and an almost completely orthogonal supply system. Orange juice and a juiced orange may have almost nothing to do with each other, at this point (depending on the source, of course). The reason I say this is that I think it would be foolish to count on the atlantic or a national border as safety, instead, think of something that has conquered the US food market (among other markets) and will absolutely expand and conquer new territory when possible.