I'm dubious. The US didn't really do much of anything but watch and try and stay out of the fray in Egypt (Tunisia we barely even had time to react to). And when you think about it, how much can we do? Ultimately, any revolution is going to be in the hands of the people revolting -- it's their concerns and their conditions which dictate the course of the movement. Except where the US can credibly threaten to intervene militarily -- implausible in all the countries we're talking about -- there is very little we can do to influence the situation, at least overtly.
Actually, I think there is one very simple reason why Egypt succeeded where Iran failed. As LGM put it, the Tank commander said "no":
Last night, a military officer guarding the tens of thousands celebrating in Cairo threw down his rifle and joined the demonstrators, yet another sign of the ordinary Egyptian soldier's growing sympathy for the democracy demonstrators. We had witnessed many similar sentiments from the army over the past two weeks. But the critical moment came on the evening of 30 January when, it is now clear, Mubarak ordered the Egyptian Third Army to crush the demonstrators in Tahrir Square with their tanks after flying F-16 fighter bombers at low level over the protesters.
Many of the senior tank commanders could be seen tearing off their headsets – over which they had received the fatal orders – to use their mobile phones. They were, it now transpires, calling their own military families for advice. Fathers who had spent their lives serving the Egyptian army told their sons to disobey, that they must never kill their own people.
Thus when General Hassan al-Rawani told the massive crowds yesterday evening that "everything you want will be realised – all your demands will be met", the people cried back: "The army and the people stand together – the army and the people are united. The army and the people belong to one hand."
And that's the key difference. Protesters rarely stand any chance, pound-for-pound, against a halfway decent state military apparatus. The question is whether, when push comes to shove, the military is actually willing to crush the demonstrations violently, or whether they link up with them. In Egypt, they weren't willing to fire on their own people. In Iran, they were. And so we have our different outcomes.
In any event, we're going to get a bunch of new data points on this shortly. New protests are emerging in Libya, Yemen, Bahrain, and Iran again. Obviously, I hope for the best in all of these countries. But I think the ultimate outcome is not likely to be contingent on what Americans say or do. It has to do with the nerve of the protesters, and the ultimate decisions of the country's military forces -- to join the revolution, or crush it.