Yes but not by a very wide margin. [1]
Average BMI in the US is 28.5, Saudi Arabia is the same, Mexico is 28.1, New Zealand is 27.9, UK is 27.3, Canada is 27.2.
My point is that the impression that the US is unreasonably fat compared to the rest of the world is mostly just bias.
[1] https://en.wikipedia.org/wiki/List_of_countries_by_body_mass...
Some people seemed very very fat.
Edit found something that would support that idea.
Proportion of people who are obese over the globe: https://ourworldindata.org/grapher/share-of-men-defined-as-o... https://ourworldindata.org/grapher/share-of-females-defined-...
Walmarts are everywhere, there are thousands of them and millions of people in them every day. You're going to see the best and the worst just because of sheer numbers.
Not saying that the fatest American isn't fatter than the fatest Australian but "people of walmart" is a bit of a misnomer because you only need one picture of a fat person in a Walmart and there's literally millions of opportunities each day to see that one example.
This shows IMO in obesity rates - they are significantly lower in London than the rest of the UK.
It is not as entirely car dominated as the USA, but I think it's pretty fair to call it "car reliant".
The other major factor is wealth. Richer people can afford higher quality food. Poor people generally consume more calories from junk foods and sugary drinks, which are staples of drive-throughs and fast food chains.