We are still in a cold war, only now it's more complicated because more countries have nukes...including North Korea which is kind of a wildcard.
Check out Nuclear War by Annie Jacobsen. It's a well-researched and horrifying scenario where deterrence fails because N Korea launches on the US. it takes you step-by-step through the decision process our government would take in response. Its gripping and pretty damn terrifying and shows just how delicate the whole situation is.
A great read, if very slightly outdated. Could still represent a possible future if Trump returns to power, or perhaps even if he doesn't. Either way, Arms Control Wonk podcast is an entertaining and informative listen for anyone remotely interested in this topic.