The US did not spend $5 billion to destabilize Yanukovich, as is popularly believed in certain CT circles. The claim came from this video of Victoria Nuland at the UK/Ukraine Foundation on December 13, 2013:
Unfortunately, she did not say what the CT sites said she did. The relevant portion begins at 7:26. However, when she talks of the $5 billion, it is money that the US has spent since 1991 aiding Ukraine since they became independent building up its democratic institutions. This includes plenty of administrations that were pro-US. We do know from the infamous "Fuck the EU" phone conversation that Nuland and the US were a lot more involved in forming the coalition that toppled Yanukovich than was popularly believed.
Had the $5 billion claim been true, it would have been a smoking gun. It is believable given the US propensity for spending money to undermine governments; currently, Venezuela. It would have established the US as an instigator. There are still questions that remain about the US role in Ukraine. When did the "Fuck the EU" conversation take place?
In the absence of any concrete evidence otherwise, Yanukovich along with Putin were the instigators of this conflict. Yanukovich backed out of an agreement with the EU that had been 5 years in the making, instigating this conflict and triggering the Maidan protests. Later, he made it worse by outlawing protests and firing on protestors. And Putin made it even worse by sending troops and tanks into Crimea after Yanukovich fled. We await a smoking gun implicating the US as chief instigator.