Things the US can do:

1) It does have to overt
2) Becasue we need to send a strong message to Russia.
3) We can have a large UK/EU/USA fleet in the Mediterranean and can sail for Turkey on the other side of the Strits. That isa large nava/air presence.
4) We have not withdrawn our training officers and 1000 troops that are there and will not do so. They are in Gori and Tbilisi. If the Russian try to take them it will be an act of war against the US.

5)US will not go to war over Georgia. Risks are too high and we are a nuclear power. But we can without words threaten with a presence nearby.