AFAIK, and feel free to correct me if I’m misremembering, but the Soviets never did have a lot of boomers close to the US…just a handful. Most of their boomers were closer to their home waters where they could protect them from our attack boats. So, assuming my memory serves, I don’t think the US was ever in a lot of danger from Soviet SLBMs (the converse wasn’t true, since our boomers were all over the place and ready to hit them if the balloon ever went up).
Even a 200kt warhead is only going to have a high-casualty blast radius of a few miles. Most people would survive even a three-way full exchange between Russia, the US, and China. These days there just aren’t enough warheads active and ready to go to “wipe out all life on planet earth 15 times over” or whatever they used to scare little kids with. I certainly wouldn’t want to be in the center of a major city or on a major military installation, but other than those places, lots of people would survive.
You’re ignoring things like wildfires and nuclear winter.
Yes, and starvation and dehydration and illness. Certainly losing most major urban centers would immensely complicate life for the survivors. My post focused on the initial blasts, and perhaps the immediate dangers of radioactive fallout. Too many people adopt a “well, if it happens we’re all screwed anyways” attitude that doesn’t square with the reality of it. Much like early Western settlers though, there would be immense challenges afterwards, and surviving those would require a combination of hard work, preparation, knowledge, skill, and luck.
Which is why civil defense planning wasn’t/isn’t pointless in the nuclear age. 
Nuclear Winter balances out Global Warming. It’s a win-win.
Belfast is a major UK political, economic, industrial and military center. How do you say “buggered” in Irish?
As for the republic, depends on the political situation. Cork and Shannon airport are likely targets, in any case.
To die of disease and starvation in 6 months or less as their supporting infrastructure is also destroyed.
Most people on the planet would survive the immediate effects of a strategic exchange. Most people in the US, USSR, and China would not survive said exchange. A high-casualty blast radius of a few miles covers the major metropolitan area of most cities. Now replace that single 200kt warhead with say, a single 25Mt warhead (SS-18 mod 1 and SS-18 mod 2) or even better and more likely, figure say 4 or so 100-200kt MIRVs detonating at different locations above said city. Want an idea how bad a 25Mt airburst is? Try it out here; I popped one over center city Washington DC. The 5psi air blast radius (most residential buildings collapse, injuries are universal, fatalities are widespread) extends to North Bethesda. The thermal radiation radius (danger of 3rd degree burns) extends out to Annapolis. This is of course only counting the effects of the initial exchange; the survivors have famine to look forward to.
I have no idea where you get your ideas from, but they didn’t try to scare little kids with being able to “wipe out all life on planet earth 15 times over.” What they talked about was the level of overkill in the size of the arsenals being such that the US and USSR could wipe each other out dozens of times over. SIOP had 16,000 targets for US and NATO warheads in the National Target Base in 1985.
The US wasn’t in a lot of danger of SLBMs being launched from Soviet boomers right off the US coast leaving little to no warning time, but the US was very much in danger from those SLBMs when they got the order to launch. Conversely US boomers couldn’t launch on Moscow with little or no warning time no matter where they were located due to how far inland Moscow is. Soviet doctine for their SSBNs was to keep them in bastions in the Arctic and Sea of Okhotsk in the Pacific where they could be defended by their own SSNs and other ASW forces. One theory mentioned in the linked book is that the bastions were part of a “withholding” concept whereby the SSBNs would be employed in a second-strike capacity.
Don’t forget massive worldwide ozone loss: http://www.pnas.org/content/105/14/5307.abstract
A long time ago I read in some fictional nuclear apocalypse scenario about something called “death rattle”. In this context, it was that supposedly there could be a second nuclear exchange days, weeks or even months after the primary exchange. The idea was that there might be surviving nuclear reserves- ballistic submarines in hiding, silos that survived the first exchange, bombers sitting at dispersed desert sites and (in the Soviet Union) land-based mobile missiles. That these forces would have default orders amounting to “if you haven’t received any further orders by x-date, launch at these targets”. Is there anything to this?
For the UK at least this is sort of the case; upon taking office the incoming Prime Minister writes four identical letters of last resport:
See also Dead-Hand for a Soviet fail-deadly system of automatic nuclear retaliation in the event the leadership who would normally make the decision is destroyed. Remember the doomsday device in Dr. Strangelove?
This. Back in my civil engineering days, my boss actually had an old engineering manual for designing for\surviving nuclear blasts. Obviously nothing is survivable at ground zero. Then again, every nuclear bomb isn’t a 50 megaton Tsar Bomba. A few miles away for most bombs is pretty survivable if you are underground or in a concrete structure like a school. Ducking under a desk is to protect you from broken glass, not a thermonuclear shock wave.
Now you might not survive the radiation, nuclear winter, mutants and roving gangs of cannibals that follow. My boss didn’t have a manual on that though. That’s some other guy in another department.