I've had a frustrating form of this conversation with so many Americans. The concept of buying less than 40L of soda at a time, because presumably they drink many liters per day, is hard to overcome for some.
They literally will not believe that it is possible to but a days worth of groceries every day, and get fresh, quality food.
But the more people saying that it can be done, and is a superior way to shop, the more likely we will convince them finally.
You're really comparing apples to oranges because the majority of Americans don't live within reasonable walking distance to a grocery store to begin with. Depending on where you live, it's not uncommon to take 15-20+ minutes to drive to the closest store.
With the return trip time + parking, you can see how it's much more sensible to plan your shopping ahead of time to optimize for the fewest amount of trips possible.
Even if you currently live in a borderline walkable area, there's a solid chance you grew up in an area where driving to the store was a norm and thus contributes to the decision to walk vs drive.
Agreed on the design of most grocery store in the US. Most people can't stop in quick on a normal daily walk, because the inherent space-inefficiency of cars means a long detour to hit multiple stops, whereas with walking it's an easy in-and-out grab.
However, even when patiently explaining this difference, it is a mental leap too far to consider any change. Not only is it the physical design of the stores and car-only infrastructure, a lot of it has to do with package sizing and pricing structure, as another poster pointed out; smaller quantities get massive markups in US stores, for no good reason other than once they've got you in a store, you're fairly captive and they want to extract the maximum amount of money from you so that you don't end up elsewhere.
Until people experience it, and realize that having a five person family is no challenge at all for this style of life, it's hard to give them the picture.
In most American cities, going to the grocery store is kind of a pain. You have to drive somewhere, usually at least a mile or two. You have to find some place to park and walk across a huge parking lot. The store itself will be huge, if you're just getting three things you have to trek all the way across the store to retrieve them. And the lines at the checkout can be bad.
As I mentioned in another comment, I had the opportunity to live for a year in a very walkable neighborhood, with an excellent grocery store. It was convenient, it was small, the food was high quality, checkout was lightning fast. I found myself going there nearly every day and it was wonderful.
But once I needed to move back to a more car-centered city, the idea of doing this became once again unthinkable. Far too big of a chore to do daily.
They literally will not believe that it is possible to but a days worth of groceries every day, and get fresh, quality food.
But the more people saying that it can be done, and is a superior way to shop, the more likely we will convince them finally.