Enough? Enough for what? This is not mutually assured destruction. If Russia and the US engage, this is a madman shooting a tank with a 9mm. It may cause some damage, but he's going to be obliterated in the process.
I don't know, losing for example New York City would be kind of rough. In reality probably every major US city.
Your analogy doesn't quite check out.
Any large exchange of thermonuclear weapons is going to break most supply chains and lead to a great simplification of society and the deaths of at least 90% of the population in the process as industrial farming stops being a thing.
But nuking Russia is still bad since it would cause trouble (nuclear winter for example?) for other countries/whole world