P.S. For all national politicians and administration representatives, we shouldn't forget that foreign policy is sometimes domestic politics via lobbying groups of American citizens of various heritages.

 Agreed, but in this case I very much doubt the speech was made as a play for the American Ukraine vote.

I thought of this right away with Lulu's video link, it's was a speech to the U.S. Ukraine Foundation. That's like giving a speech to AIPAC. What someone says to AIPAC or any similar organization is usually spun to make them happy and one must be careful not to take it as whole truth about actual policy.

 I think listening to a leader's speech before a group that has a particular agenda regarding the issue at hand can be very helpful but I agree that one person's speech cannot always be taken as their government actuall and total position. I think your comparison to a speech at AIPAC by an American politician is particularly apt and I thought of it myself but was hesitant to make it for fear of radically diverting the conversation.

Unlike AIPAC, I have not been able to find out much about The US Ukraine Foundation's lobbying goals but I assume they are aligned with one side or the other in the deeply divided positions held by the various groups whithin Ukraine as made clear by the maps recently posted here and in other ways.
Among other things, Nuland's speech is obviously intended to show general alignment with USUF's position and, like a US official's speech before AIPAC, it is intended to send a message to many people and groups beyond the ones in the room. So, it is definitely taking a side but in this case not honestly, IMO.
 Again, ignoring the strong divisions of sentiment in Ukraine, Nuland talks as if the entire county's wishes were in alignment with a desire to overthrow of the current government and a move towards the EU and away from Russia. At one point she actually describes peaceful demonstrators, the only kind of demonstrator she acknowledges to exist, as sitting around singing hymns of peace when the authorities opened fire on them.  I believe that reading a transcript would reveal her strong bias and willingness, actually I mean her intention, to misrepresent the situation, but listening would make it even more obvious.
 Nuland very strongly and very explicitly says that it is the hope and intention to bring Ukraine towards the West and away from Russia. Fair enough if that is a legitimate policy and if the reasons to do so are honestly expressed BUT that expression, by itself when done by the U.S, is powerful enough to be considered meddling in the internal and local affairs of a foreign government. Handing out cookies to the protesters during a potentially explosive standoff with their government as they confront that government is itself meddling which would be strongly condemned and probably halted if done by a foreign ambassador hostile to our government and done in front of the White House. It is messaging of support for various groups who are in some cases sharply divided among themselves but it is obviously not all the support that has been offered or implied.  
 Following your third link above and also other articles at the same place make it clear that the Ukraine was made an offer by the West that it could not accept for political reasons and because of the many strings attached. If that is a fair conclusion then I think it is fair to believe that the offer was made with that understanding.
 Results of the political mechanizations play out among the population but the policies originate among small groups. I seriously doubt that the weight of the citizenry of the EU strongly favor bringing in Ukraine to the EU and I doubt doing so at any time in the near future would help stabilize anything.

One thing that encourages blogging by halfway informed people like myself is that there is always someone somewhere with some amount of established credence [with at least one or two people] that takes what is at least approximately the same position.     How's that for a boatload of equivocation in one sentence?

American neocons helped destabilize Ukraine and engineer the overthrow of its elected government, a “regime change” on Russia’s western border. But the coup – and the neo-Nazi militias at the forefront – also reveal divisions within the Obama administration, reports Robert Parry.

Thus, the Ukrainian coup could become the latest neocon-initiated “regime change” that ousted a target government but failed to take into account who would fill the void.

http://consortiumnews.com/2014/02/23/neocons-and-the-ukraine-coup/

Most everyone's mileage will no doubt vary.