I come from a small town an hour from Houston, Texas. In the 1970s, a regional chain called Howards BrandDiscount moved in and soon drove most of the "mom and pop" dry goods stores out of business. In the 1980s, Kmart built a store up the road and soon drove Howards out of business. In the 1990s, Wal-Mart built a little further up the road and soon drove Kmart out of business. They used the power of their other profitable stores, which allowed them to operate at a loss and under-price the competition, until this was accomplished. Now they are about to build a new Super Wal-Mart yet further up the road.
Also, there was once a popular grocery store called Minimax in the same town, which was a locally-owned franchise. An aggressive regional chain called H.E.B. Pantry came and told the owner to sell the store to them, or they would build down the street and drive them out of business. They sold out. Now there is just one other full-service grocery in town, another regional chain.
I expect the Super Wal-Mart, which will include groceries, will drive the other groceries out of business. There are not many jobs in town these days except low-wage retail. Soon they will become like one of those infamous "company towns" where one can only shop at the "company store."