Today I'm comparing the US and UK covers for Sharpe's Fury, the most recent entry in Bernard Cornwell's long-running series about the adventures of a British army officer promoted from the ranks in the opening decades of the 19th century. As with the Novik series, these are books that I adore and highly recommend, though Fury wouldn't make a good entry point, IMO--better would be Sharpe's Tiger, the first book chronologically (though not the first published), or Sharpe's Rifles, the first of the Peninsular War stories.
Both of these are, IMO, decent-to-good covers. Not the best I've ever seen, not even my favorites from the series, but they match the contents of the story (mostly--see my comments on the UK version below), and I certainly wouldn't feel any embarrassment at reading them in public.
In this case, the biggest US-UK difference is obvious: redcoats. They're a prominent element of the UK cover, while they're almost entirely absent from the US version. Which makes sense, because even though our countries are pretty much Best Friends Forever now, it's hard to get completely past the associations American children pick up in our elementary school history classes that redcoats are Other, even if you're happy to be reading novels all about the British army of the Napoleonic era! (I think I'm about 99% past those associations, but I'm a military history buff who's studied the era as inspiration and setting for my own writing. In other words, I'm not at all typical.)
Another somewhat more subtle difference is that there are more people on the UK cover, and none of them really stand out, while the US cover focuses on the hero. Since I've noticed this group vs. individual distinction on multiple US vs. UK covers across several genres, I think it's reasonable to deduce that this reflects the hyper-individualism of American culture.
(In the interest of giving credit where credit is due, all my thoughts on cultural differences on both this and the Novik covers arose out of a conversation with my husband, and the ideas are as much his as mine, if not more so.)
As for my own opinion, again, I like the American cover better, for reasons that I'm sure reflect just how American I am. When I see the British cover, my first thought is, "Where's Sharpe?" Well, on the American cover, he's right there, front and center, the focal point that my eyes are drawn to. It just makes sense to me that the cover of a book should focus on its central character, and all the more so when that character is a sexy man. (OK, so my preference for the American cover also reflects the fact that I'm a heterosexual woman. So sue me.) I don't claim 100% consistency in this area, by the way--some of my favorite covers, including my favorites from the Sharpe series, don't feature people at all. But when it's a crowd vs. an individual, the individual is almost always more intriguing to my eyes.
Also, I like how the American cover has the darker illustration on top and the lighter panel with the author's name below. I don't know if it's a typical American taste or just a personal quirk, but I like strong contrasts like that--they just catch my attention.
Last but not least, the British cover pings my "nonfiction" sensors. (This is what I meant above in saying the cover doesn't quite match the contents of the book for me.) I have a shelf full of books with similar covers at my house--namely, the military history collection I'm building. To me, that kind of illustration belongs on a history of a battle or a regiment, not a novel about a character's experience set within that history. I'm not saying the cover actually confuses me--being a fan of the series, I instantly recognize the author and character's names, after all. But there's just an eensy bit of gut-level dissonance.