We have enough Airlift capacity to get food to tons of places around the US.
Military Airlift Command - Wikipedia
People can survive off of Rice and Beans. And many water supplies won't be affected by lack of bridges. Personnel will be moved to man the powerplants by Helo.
Does not even begin to approach the amount actually needed. You would need to helicopter in the equipment to build the emergency runways to land the planes next to the distribution centers, and then you need yet more helicopters to transport the good from the airport to the local distribution points. This needs to happen on a national scale as every single city, town, and village is hit simultaneously.
We don't even begin to have the air transport to move food on the scale required.
Manhattan alone has a population of ~1.7 million people. At a mere pound of food per day you are looking at airlifting in 1.7
million pounds or 850
tons. That is six C-5's fully loaded each and every day just to feed one island of one city. We only built 131 of them.
Even seizing every commercial airplane in the US and dedicating them all to food transport, you are still woefully short of what we would need. And again, that is just to go from runway to runway. Most airports aren't ideally situated for acting as distribution centers when all the bridges have gone away. In the majority of cases, you are going to have to use a chopper to get the food to the runway and from the runway to the grocery store/local drop off point.
How many transport choppers do you think we have?
And all of this has to happen immediately. Because the first thing that is going to happen the instant it hits cellphones that all bridges are gone is that everyone with a brain is going to run to the nearest grocery store and start stuffing everything that they can grab into their cart to buy it all before the stores start limiting purchase amounts. Within an hour of it happening, there will not be a single non-perishable food item on the shelf of any grocery store in the nation. Then you have all of the riots and general chaos as parents suddenly find it difficult to impossible to get home from work and kids find it difficult to impossible to get home from school. Every roadway is going to end up effectively impassible because of abandoned cars.
You need airlifted emergency food shipments to every single city and town in the US going out literally day one.
And all of that is also ignoring the other issues, like getting the soldiers to base in the first place.
If you don't already have enough cultivated land to feed your family or enough stockpiled to last until you can bring in the crops and the needed skill & tools to grow your own food then you are most probably dead.
This also ignores the thorny triage issue. Every single city has become a death trap and will breakdown inside a week. Letting the cities starve and using the available transport and people to distribute food in the rural areas is the correct choice.