l guess a factor are also the different local habits for doing groceries.
Here in our home town in Germany we have three mid-sized full-range grocery stores within walking distance, so typically do shopping 3-4 times a week.
Makes it much easier to shop fresh products and stuff with more limited shelf life (this demand causes easily availability for these).

As I understand shopping in the US, it seems to be more typical to go shopping only once a week or so to the far away mega-store, making it less viable to buy much fresh stuff and also increases the need for products that have been treated to ensure longer shelf-life.

Yep exactly this. Even though the grocery store is extremely close to my house, it’s the only one, it’s still not a reasonable walking distance for trips 3-4 times per week, and the food is exactly like you said, mostly treated.

I’ve been to several places in Europe and the grocery situation there is so much better, it’s honestly astounding.