In the first place Georgia started the fighting be sending their Army into S. Ossetia where separatists wanted to join back up with N. Ossettia which is still part of Russia. All the Russians have done is responded by invading those areas of Georgia where the populations are more ethnically attached to Russians.
What business is this of the US? None until you consider the geopolitical situation. There is the belief that the basin around the Caspian Sea holds a lot of oil, and if you don't want to deal with Russia or Iran to get it, the fastest way to the West is through Georgia. It is clearly in the West's interests to keep Russia and Iran from controlling the oil flow to Europe.
The real question is, why did Russia respond in the way that they did? Georgia was part of the USSR and they let it go. You can bet at the time the Russians were careful in terms of what they gave up, but it appears that Russian dreams of being a world power are far from dead and maybe they have other ideas about their former satellite states.
One would think that the two neighboring states would get along reasonably well, but Russia is becoming more imperialistic now that their oil and mineral wealth has put them into a position of influence. Russia is still a dangerous state. They may not be Communists any longer, but they're have no respect for private property and the rule of law. They seem more interested in flexing their muscles and seeing what they can get away with.
And this thread has turned into a discussion about Tron? No wonder the US is going down the tubes!