In addition to being overweight, there is the problem of your posture getting stuck in a position if you are always in that position. You know how in other countries people take public transit and walk or bike places? This allows the posture to reset after sitting at an office. Americans never get that chance because they go from sitting at the office to sitting in their car to sitting on their couch. So their neck and shoulders never really gets much of an opportunity to not be pushing kind of forward. Add to this that they are often looking down at their phones and you can imagine how the combination of these two postures can result in a thicker appearing neck.

Edit to also add to this: Americans are also on the higher end of the average height globally. This means if you take a picture of one, there is a better chance the American will be looking somewhat downwards at the camera, which also increases the size of the neck. If you interact with Americans in real life and you are shorter than their average height, this perception trick will also happen. It's one of the many insidious ways we maintain our dominance over other countries. 🦅🦅🦅🇺🇲🇺🇲🇺🇲