Like many things in Canada,
most grocery stores here are owned by one of 3 Canadian corporate giants. We love our oligopolies here. Our internet & mobile situation is very similar - most carriers are owned by one of 2 Canadian corporate overlords.
No doubt you haven't heard of most of our grocery chains, because those who own them would be hard pressed to deal with actual competition. I haven't done any research on this, but I wouldn't be surprised if they just haven't bothered to expand into the U.S. much - or they tried and failed to really gain a foothold. They stick to Canada because they have little competition here, and our political class ensures that entry into the market by an outside corporation would be very tough. For most American grocery chains expansion into Canada would probably be way too much hassle, and not really worth it.
Walmart and Costco are the two exceptions. I suspect they were able to crack into the Canadian grocery market because groceries are only a part of what they sell. They are also corporate behemoths with plenty of corporate muscle to weasel their way into the Canadian oligopoly paradise.
I took a look at the lists and the only ones I've ever shopped at are Sobey's, IGA, and Stupid Store (people who have never run into their ableist attitudes toward disabled people might still refer to it as "Superstore").
IGA closed here, which is a shame. It was a great location in the middle of downtown, and very convenient. I think there's a dollar store there now.
There's a Sobey's within a short taxi ride from here, but their prices are too high. And it's a strip mall kind of locale, so not very appealing for me. Somebody killed a doctor at the local walk-in clinic near there a few years ago (used a machete).
Stupid Store? I hate that place. I hate the snooty staff, the way the cashiers don't give a damn that some people can't bag that fast, and that they don't understand that there are valid reasons for bringing more than a purse or wallet with you into the store, particularly if you use mobility aids and can't carry stuff. And then the situation that happened when my dad's girlfriend died... she had a credit card there, and I guess it was maxed, or she wasn't making payments, and they decided to harass us about it because our address was the one she'd given as her mailing address. I told them that she was no relation to us (thank goodness they never married and their relationship didn't fit the legal definition of common-law), and we would not be responsible for her debts. When they asked for the next of kin, I told them her son in Ontario would be their best bet. No, I had no address or phone number. Then they threatened to repossess her stuff. I told them that if they gave me a time and date, I'd take her stuff to their office and dump it out on the floor and they could take what they wanted and junk the rest. They finally quit hassling us. And I've never stepped foot there since.
I do most of my grocery shopping at Walmart now, some at the Co-op, some at London Drugs, a little at Dollarama, and a tiny bit at Save-On (depends if I've gone for a flu or covid shot and have a few minutes to kill). My local Walmart is in a mall, so there are other places to shop at and places to rest. The mall has a small veterans' museum open now in a vacant store (don't recall what used to be there; half the spaces in that mall are empty).
I try to stay with familiar places, because having unreliable eyesight means it's stressful when trying to find stuff. I didn't get half the stuff on my list earlier today because I either couldn't find it or they were restocking the shelves - leaving NO room to get around them with my walker.
Here's a thought... could they not do this BEFORE the store opens? Or would that just make too much sense?