I've only read RSR . . . the others have been movie adaptions and although I did thoroughly enjoy some questions did pop into my head.
Would it have been so easy for the Soviets to take Iceland?
Assuming the premises of the book, I think so. Even Germany in WWII could do, I think, with a surprise assault using false flag cargo ships. The problem would be keeping it, in the face of enemy air & sea superiority.
What baffled me though is why didn't NATO forces land in the Faroes and attack AVMF long range aircraft (Bear, Badger and Backfire's) from there using the Nimitz's F-14's instead of Scotland?
Why didn't the Soviets land in the Faroes's as another string in their bow thus putting more pressure on NATO convoys by launching AVMF aircraft from there?
How and where? Afaik, there's one airport in the Faroes, with one runway. Not enough to support the dozens of aircraft required, not to mention the need for support and supply infrastruture. For the soviets this would be agravated with the need to airlift an assault & ocupation force, and maintain it.
Why didn't the US Pacific Forces go on the offensive in the East attacking Soviet defenses and tying Soviet Forces up in the East?
Cause the book is Europe-centric.
And above all . . . what would've happened to other countries around the world without having the US policeman around? . . . . wouldn't North Korea try it on?, wouldn't the Arabs settle a few scores with Israel?, even Argentina would be encouraged to have another pop at the Falklands as the RN's forces are tied up in the North Atlantic.
This could've ended up with a greater novel (more pages) or even splitting the novel into two possibly three books.
You're right on "more books"; you have stuff for 4-5, what with imediate consequences and future ones. For example, I doubt even North Korea could just shout "banzai" and gogogo; and, at the first shot in Europe,
South Korea would be sure to go into high alert. Argentina would certainly eyeball the Falklands but, at this time (1986) it was still mid-post Falklands mess, with it's navy and air force wrecked. Even a diminished Falklands garrison would be enough. The rest of South & Central America, most of which at time was a dictator of same kind? Now,
that would be a mess. Left wing movements are sure to be emboldoned to attack right wing governements, who would in turn feel they had their hands free (and the backs to the wall...) to press down harder...
Arabs vs Israel? Again, the issue of preparation. Israel is still trying to get out of Lebanon, so it's armed forces are in high(er than usuall, that is) alert. Syria has an itchy trigger finger, but the airforce still has the Bekaa valley in mind. And, now with full control of the Golan Heights, Israel has an advantage over the area, As for Egypt, not only it has (apparently) calmed down, at this time it's very much on alert because of Lybia (re: post 1977 war tensions). King Hussein was trying to keep Jordan out of the overall conflict, barelly "showing up" for the Yom Kippur war; there's evidence he did it only to save face, to keep the status quo with other arabs. Saudi Arabia and the gulf states don't matter, and Iran / Iraq are at each other's throats.
My guess is that Clancy just wanted the classic "WWIII starts in Europe) scenario and roll with it. He clearly knew how messy the whole thing would be, so he kept it simple(ish), going for the whole "short victorious war launched by side A" story that always works so well...