There was a case study I read in some supply chain courses a while back that was about supply disruptions in supermarkets due to a temporary but unforseen border closure somewhere in Central Europe. I don't remember exact numbers, but the relationship between the number of missed supply trucks and products out of stock was roughly exponential. After a single truck, there were like a dozen products out of stock. But after a second truck, there were over 400 products out of stock. By the fifth missed truck, 20% of the entire store was out of stock.
Since most stores have distribution centers that can break up replenishment into small increments, grocery stores typically use a method of inventory management that "tops up" inventory levels on a scheduled basis. High demand items might get replenished once a day or more, while some might get replenished on 2, 3, 4 day intervals all the way up to monthly intervals for low demand durable items. Replenishment schedules are staggered on a per-SKU basis, so that the number of trucks per day is roughly constant.
The short story is that delayed trucks might be a tiny annoyance, but a full supply disruption can cause utter chaos in less than a week. If reroutes through the US aren't facilitated, you can expect to see all of the most commonly purchased items in your grocery store out of stock far sooner than you expect.