Television programmes

The death of Mattie makes more sense at the end of series one than the death of Zoe at the beginning of season two in the US version. But it didn't really come across as a surprise when Mattie headed up to the roof; it was fairly obvious what was going to happen, mostly because I had seen the US version.

in the UK version he is PM by end of series 1- but he still has the monarchy to deal with (the subject of series 2). The US, not being a proper country, has no monarch, so if he had become President in the first series there would be nowhere else for him to go.
The death of Mattie worked for me. I was shocked by it first time I saw it. For me it worked in reverse, I was surprised when it didnt happen at the end of season 1 in the US version, and unmoved by it when it did at the start of season 2.

The progression of FU's plan is pretty much as close to the original as it can be given the different systems. By the end of the first season, Underwood is in the executive and able to start calling policy shots, but he still has to deal with the President, who is his boss. In season two, he turns on the President, who he's expected to be loyal to, and defeats him. The biggest difference is that in the UK version, the King's involvement in politics was unusual and arguably unconstitutional, which gave Urquhart an additional weapon to use against him, but in the US version it was the President's connection to illegal fundraising that Underwood was able to leverage.

The death of the reporter character wasn't going to come as a surprise to anyone who is familiar with the original. Speaking anecdotally, though, it was definitely a shocker to the rest of my family who are unfamiliar with the British version of the show. I had forgotten much of what I'd read about the UK version myself, and so while I wasn't as surprised as them, it definitely caught me off guard.

I think the death is more shocking in whichever you saw first. But I felt it was better placed at the end of a series rather than the start of the next.
I had assumed they must have thought of some further involvement for her which was why she had not been killed off as in the original, so I was somewhat surprised still she died immediately anyway.
A friend and I had a lot of fun speculating on how the US version would deal with series two and the Royal aspect and the solution they come up with was really the only feasible way. In effect they are both still about the same thing, trying to topple the Head of State.

Another difference I noticed in the character of Francis is that the UK version he seems to have a much clear vision from the very start of how he wants the country to be, the sort of PM he will be, the sort of policies he will enact. Whereas in the US version you get the sense of a man slighted, and you get the underhanded viscous thug he really is under it all, but you dont get a sense of his own self belief in his destiny anything as strongly. And for me iot makes the character less interesting.
There is a self awareness to the UK version as well, such as right at the start when he tells his wife that the local party people were saying he should run for PM, and he quotes Macbeth, "Glamis, Cawdor and King hereafter."

I can see how the death was disappointing since you were expecting them to depart from the original, but I think that for someone watching the show with no prior knowledge, a death that early in the season (particularly since they featured her prominently in the advertising) was plenty shocking and dramatic.  They built up the Russo character (analagous to the PR director in the British version) significantly and so I think his death was more emotionally significant in the story than O'Neill's, and thus following it up so quickly with another murder would have diluted the impact of both.

I agree that Underwood in the US version does not seem to be interested in principles at all, or even in politics all that much.  I think he has a line to the audience in the first season where he says that he doesn't care about ideology, but watching his behavior, it's evident that he doesn't really care about anything other than acquiring personal power, even if it means he ascends to an office that is tarred with scandal, a reputation that is in tatters, and a minimum of political capital to work with.  Although I suppose he doesn't need any of those things since the writers are very clearly on his side in helping him get his way.  But yeah, much as I've enjoyed the show, these parts do bug me.