"We have to recalculate weight on airplanes" is just a proxy, a code smell. There's an iceberg of catastrophe here.
(And actually, they have also gotten noticeably heavier in Asia and Africa, too, but because they started with much lower obesity rates, it just isn't as noticeable. For example in 1975 14% of Japanese were overweight, compared to 47% US. By 2013 that was 28% Japan, 72% US).
There's a nice interactive graph on the linked page around 2/3 or so down that lets you look at the growth over time for assorted countries.
This should be pretty alarming, because it indicates that whatever is leading to soaring obesity in the US quite possibly is not something specifically that we in the US are doing wrong in our eating or exercise choices and habits.
Of course it's more complicated than that, studies are moving in that direction but it's going to be 50 more years since updated dietary guidelines become common (grandma's) knowledge.
Edit: exports
Portion sizes, excessive fat and simple sugars, loading everything (even savory foods) with huge amounts of federally-subsidized cheap corn syrup, all sorts of things. It's not as simple as (or related to) livestock practices.
There are no more normal size candy bars for sale in the gas station by my winter home; only "king size" which are approximately 2x the size of a normal candy bar. This is just one of a million little examples.
American bread is basically cake. We serve fries with everything. Ketchup, which is basically red sugar paste, is a go-to condiment. People drink fruit juice “to be healthy”, etc etc.
Even in big tech companies, nearly all of the snacks are carb dense potato chips, sugar glazed nuts, candy, instant noodles, and more.
Everyone eats like they work 10 hours of calorie-intensive labor while barely moving at all. It would be a wonderful if the only thing Americans ate was chicken and steroid milk exports.
The difference is your portion sizes are gigantic compared to ours. If you go to a McDonald’s in Holland and buy a meal, our fries are what you’d call small size, and our cola are what you’d call child’s size. At restaurants we don’t have unlimited refill of cola like you do, we pay for each bottle so we don’t typically drink an entire days worth of kcal in cola with each meal like you do. Our breakfast is smaller and cold, not big lavish feasts with cooked food. What you call breakfast we’d probably call lunch, and what we call breakfast you’d probably call a snack.
We also collectively exercise more than you do just by living. It’s not a secret that bicycling around is a huge thing and the primary transport we think of when we want to go somewhere unless we have a reason not to.
I’m sure the types of food you have are a big contributor, but at the end of the day you’re the ones stuffing all of that into your mouths instead of properly portioning out sizes.