Venezuela is also run by the same security apparatus and government as it was before. We didn't attempt to turn over the entire government.
Takes Ukrainians 4 months to kill that amount. What you are saying winning is quite doable.
First, Russians are generally on the offensive, which means pushing into Ukrainian controlled territory.
Often, they are pushing into defensive lines that have had years of fortification.
Second, there are a lot more Russians in Ukraine. To kill 125k people, you have to find 125k people. It's a lot easier to find a Russian in Ukraine that it will be to find an IRGC soldier in Iran if there's an invasion and guerilla operations in response.
In Iraq after the conventional military phase, the US killed ~26k insurgents over the course of a decade (and also captured ~120k).
Iran is bigger than Iraq, has far more people than Iraq, and has much bigger logistical burdens for an invasion.
I could believe that the US Military is quite capable of running some small scale targeted operations within Iran successfully. We can probably pull off operations to do things like attempt to seize and secure uranium stockpiles if we know where they are (though such an operation could also go catastrophically badly, too).
I think the US Military could invade Iran and topple the regime, but it would be an enormous lift, and I think there's almost no chance we would have the political will to sustain the costs and casualties that a total invasion would entail.
Which means now Venezuela is still a chavist regime, but not under US embargo anymore. This will improve their economy a great deal, and if the regime doesn't capture all the profits for itself, will also improve the QOL of all Venezuelians, hopefully.
It has little in common with Iran, which is more like the 2003 Iraq war (but, so far, without committing ground troops, but there is no way to maintain that with Trump’s stated goal of “unconditional surrender”; that’s going to require a ground forces occupation at a minimum, and probably a ground forces invasion to acheive it) than it is like the recent intervention in Venezuela.
Even if they are not particular fond of the regime that is in the process of being destroyed, the Iranian people are likely to resist that, just as occurred in Iraq (with the most significant resistance there coming from forces that were opposed to Saddam’s regime and which had been actively suppressed by it while it was in power.)
