I moved from Canada to the US a few years back, and gained an enormous amount of weight and gained a bunch of health issues, all food related. Here's my take on it.
Food is much, MUCH cheaper. Not a big difference at the grocery store for whole produce and raw ingredients (though it is cheaper). But the processed foods, premade stuff, deserts, drinks, etc? A fraction of the cost.
Restaurants are also much, much cheaper. Where I used to work, going to the sit down restaurant next door downtown brought me down 20-25 bucks. A similar restaurant downtown where I now live has equivalent food for 8-10 bucks. I make 4 times my Canadian salary and pay a lot less taxes, so effectively, it's virtually not worth it for me to cook, if my only constraint was money.
Sugar in EVERYTHING. Food that used to be a little bit sweet (not necessarily health, but not the end of the world) is drenched in sugar. I have to be careful when I get an orange juice in case its sugar added. A milkshare at the local icecream shop has way more sugar. Sugar sugar sugar EVERYWHERE.
Ordering food is also way easier, with formerly Foodler, GrubHub, Doordash, etc. I have no idea if those services became common up north after I left, but that was a big change, being able to order from 100 different restaurants at any point in time, sometimes in the middle of the night, with a few mouse clicks.
The portions: Cheesecake Factory exists up north, but it's not considered normal. Here, while the portion sizes are certainly above average, they aren't exactly unique either. You have Outback and the like all service you enough food to last you 3 days.
I also find it a lot more common to have fatty or sugary snacks at the office, and soft drinks, etc.
I'll shamefully admit I have zero self control when it comes to food. I have a sweet tooth like no other. But the price and availability constraints in my hometown stopped me from going overboard. For a while I was pretty much flush at my "recommended" weight. After I moved here? Things got really bad for me.