Such an action against Venezuela could bring oil prices up and ruin USA. Venezuela does not need to counterattack. Oil market would do.
You have no idea how much punishment the oil market can take. Any war against Iraq hit a far larger exporter of oil as Venezuela, with Saddam using scorched Earth tactics to increase the damage. Guess what, it did not harm the USA more than it harmed Iraq. No oil, no money, no weapons.
When Venezuela stops exporting oil, it harms itself. The USA only gets 15% from Venezuela. Guess how many countries will be happy getting a share of these 15% for their own profits? It would maybe create a short price spike for a week, before all oil is flowing into the USA again like planned.
Venezuela instead would loose a lot of money which it badly needs now. Oil not only runs the military, but also keeps the population calm. If Venezuela tries to export the oil to Europe, it will reach the USA again. A small increase in Oil prices in the USA, more money for Europe. But still no reason against the USA "keeping the oil flowing". Securing the oil fields of Venezuela is a simple action, and even politically not too hard. The districts of Venezuela, which have oil, are ruled by strong opponents of Chavez. The USA could practically do the same as Russia in Georgia:
1. Support separatists.
2. Become peace keeper
3. Fight any attempts to reclaim the region.
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There is a difference between Germany in 30's and Georgia now. Germany was capable of producing modern military hardware, and very much so - while Georgia, on the contrary, is not. It is a poorest country of the ex-USSR, that has been living through ethnic conflicts, power struggle and civil war all that time. One would have to invest whole lots of $$$ in Mr. Saakashvili's rearmament, and the question is, for what's good? The army of Georgia hasn't proven to be a formidable force after all training they received, as it turned out.
While you are right on the situation for Georgia, you underestimate their performance - it was enough for making the Russian actions painful enough, if the number of losses you provided are accurate. Georgia lost more, but that was never a question for them against Russia. They expected that - and the last independent news from Georgia sound like most Georgians also think that and celebrate still being there.
If South Ossetia does not prove itself worth of the action, no Gleichschaltung of the Russian media will keep civilians from questioning the war, which killed their sons. "For what are we fighting for", will be the question. Georgia has it simpler, they can claim they fight for their territory.
South Ossetia does not have anything of value, not even touristic sights (other than core Georgia or Abkhazia). Recognizing the government of South Ossetia is also something, Russia will not do. It would make North Ossetia rebel for joining South Ossetia. Russia profits only as long, as South-Ossetia only stays a de-facto state - a destabilizing moment. Any form of stability is bad for Russia as it destabilizes actually itself.
It is simpler with Abkhazia.