Mare than likely one would live only a few weeks in a world gone MAD
Nuclear Winter is a discredited concept. It was debunked even before the various SALT and START treaties reduced warhead count.
But.
It is true that most Americans would starve. Russia would win. They are more spread out.
The primary targets for Russia would be the Gulf coast and a few other places where there are refineries. If you have no diesel or gasoline, you cannot transport food. The cities would die. Essentially 100% casualties.
Ports of entry for refined product might also be major targets. The days of targeting military bases . . . well, that will still happen, but that’s not where victory is.
Victory is making your opponent surrender and starvation does that. A Democrat president, elected by city voters, would react very quickly and surrender in order to retain power.
A Republican president would find there is not much choice. He’ll take longer but will still surrender.
The Russian cities are far more spread out and distances to food sources are shorter.
They win. We lose.