I used to work for one the largest competitors of Walmart in Europe.
In France and many European countries to open a supermarket you need approval from a local and national administration. They check if your supermarket will endanger local commerce or existing big box retailers.
This is one of the reasons why Costco has delayed it's opening in Paris suburbs. All major european retailers fought (openly or covertly) against the permit and won several times.
Fear of the "big American Wolf" aside, it is a well known fact that letting a big box store or a retail park open near a busy city center will cause damages to the city center: some mom and pop shops will move onto the retail park, national clothing chains will do the same.
Once almost everything a consumer needs has left for a nearby retail park, the city center economy collapses. Once the city center starts to collapse, it drives even more consumers to the retail park in a cascading effect.
I'm on mobile atm so I can only offer anecdotal evidence but I know several economic studies have been made on that subject.
A side effect of this regulated model is the prevalence of drive through supermarkets in France. All chains have opened an enormous amount of these. The reason is quite simple: the regulation is enforced for surfaces larger than 400 square metres. Drives have at most 10 square metres open to the public so were free to set shop anywhere. It took a few years to close that loophole...and the meantime carrefour, auchan, le clerc, casino, cora all opened dozens to hundreds of locations.