I agree, there is also the fact that the US, and other western countries, could not afford another war. We can provide humanitarian aid, and look after those that have fled the country, plus sanctions, but the only reason to send in troops, would be the securing of oil reserves, just like Iraq, and this would be very wrong.
I hope that someone will just bump off Gaddafi, and without the madman at the top, support would crumble.