Psychologically? There are a number of reasons.

1. Americans - and, to an extent, the rest of the world - grew up being told that America is the home of freedom, the shining beacon of modern democracy. They also grew up being told that Russia was the antithesis of that; the evil genius sitting in his nuclear bunker, just waiting, waiting for the slightest oppertunity to set fire to some children. Russia gets less vitriol when it misbehaves because it's not as shocking - we've come to expect it from them. American misdeeds get all the flak, particularly from inside the USA, because it is so surprising. America, home of freedom, taking freedoms away is like a nun going on a shooting spree.

2. People tend to rage more at things they think they can change, and then find out they can't. It's an extremely frustrating experience. They know they can't change Russia, they don't have a vote in Russia. Maybe in Russia there are a lot of people like this guy, who hate the Russian government and fling no vitriol at the USA. Those people in the US who aim their vitriol at the US government and no others are likely extremely frustrated that they keep voting for the 'good' candidates, and everyone else keeps re-electing, in their mind, idiots. They're far more detached from the political process in Russia, so they don't care as much.

3. Put simply, perceived personal disenfranchisement is a much stronger trigger to anger than vague political disgust at something you saw on CNN.

Don't be too hard on the people who rally against the USA and give Russia a bye, they're just thinking selfishly. Yes, there are people out there that hate the USA just because it's the USA, and lots of Green Day listening teens that think George Bush is the new Hitler and nobody else could possibly be as bad, but the majority of them aren't being malicious, or even being particularly stupid - they're just not thinking things through.

So now you know.