There are 60 commercially operating nuclear power plants with 100 nuclear reactors in 30 states in the United States.
Imagine each reactor melting down and turning into a Fukushima. That is what will happen if the US suffers a catastrophic infrastructure failure. Very few would survive in a USA covered in radioactive waste.
I worked in a nuclear power plant for years. You know in the US and Europe any little glitch (and I do mean glitch) and the reactors shut down automatically. In fact, the most difficult thing about running a nuclear power plant is keeping the reactor online because they've built so many fail safes into the systems. I guess I could come up with some reactor melting scenarios, but they are so extreme, the probabilities are vanishingly slim. Not quite zero but so close you couldn't see the difference under a microscope.