Four Interstate highways connect the New York City area with the rest of the country. A fifth Interstate (I-84) is on the northern edge of the NYC metro area. If truck drivers decided to shut down or block vehicle delivery traffic into the area, all groceries would be emptied within a week. There aren’t enough police or National Guard to control the rioting. This is true for every large metro area, even more so for the West Coast cities.
Oh I would guess there is way less than a weeks supply of groceries in NY City. With just in time delivery and the costs of cold storage I’d guess the stores would be emptied overnight as soon as people realized there was a blockade. Topple a couple of high tension lines at the same time and watch what civilizational collapse looks like. The Brits were able and willing to queue for years during the war and more years after. We can’t get Americans to queue on Black Friday and that is one day.