These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Dropped a Bridge on Him: Robby Jackson is said to have become president in his own right and then assassinated by a member of the KKK. This happens between books and is only barely mentioned in passing. Some of the newer books have tried to make this more meaningful by having it be one of the primary motivations for Jack running for president again, but still...
Ensemble Darkhorse: John Clark, who is probably Tom Clancy's most popular character (even moreso than Jack Ryan).
In the opening chapters of Command Authority, a Russian operative says that the Russian President Volodin will order the Russian military to invade Ukraine and annex the Crimean peninsula. The novel was published in December of 2013. Three months later, Russia invaded Ukraine and annexed Crimea, using similar methodology to the book invasion (imported "protesters" used as a causus belli).
A big one here: Clancy was going to write how terrorists hijack planes and fly them into buildings, but his editor rejected it for being too farfetched. Clancy was actually interviewed immediately after the 9/11 attacks where he brought the idea up with one of his general friends. When asked if the idea had ever been considered the general thought and basically said, "No Tom, I don't think it had, but at our next meeting it will be."
Jerkass Woobie: J. Robert Fowler isn't a particularly likeable character but it's hard not to feel sorry for him when you take into account what happens to him. First, he loses his beloved wife in a long drawn out battle to multiple sclerosis which drains him of most of his humanity. Next, his election to presidency, an election that both he and Arnie Van Damm thought had been a close battle, turns out to have been engineered by his opponent to coverup an illegal American invasion of Columbia. Two years into his term Fowler and Liz Elliot, his new lover and National Security Adviser, then completely botch the responsive to a nuclear terrorist attack on Denver to the point that they nearly cause World War III. Then, in a fit of rage, he nearly nukes an innocent city before finding out that the terrorists lied to get America to start a war with Islam. Consumed with guilt Fowler resigns from the presidency in disgrace. As if that weren't bad enough, the only hallmark of his presidency, a peace treaty between Israelis and Palestinians, falls apart after he leaves office.
Nightmare Fuel: Though Clancy points out in his afterword to The Sum of All Fears that he specifically changed a lot of details on creating a nuclear bomb, he also points out that the information necessary to do so is public knowledge, and not terribly difficult to acquire.
Sequelitis: Ever since the end of the U.S.S.R as convenient baddies and as the books' discussion of US Politics, some feel the books have become more of a platform for Clancy's conservatism, at the expense of story.