Russia’s reasons for attacking Georgia.
1) They are legitimately concerned about the welfare of the separatist regions of Abkhazia and South Ossetia.
2) Georgia had recently launched a campaign into these regions and Russia decided to get involved in a big way.
3) They are concerned about US meddling in their border territories. (eg NATO)
4) They want to send a message to the rest of the world that they are willing to very active in their territories.

Frankly, I dont think we (the US) should get involved in this region as it would be better to improve relations with Russia then piss them off.