Answer: American revolution is in fact a building of a totally new society, on a new continent. That is the most essencial difference in comparison to French and Russian revolution. Of course everythings takes place within British ideological and political context, but colonies are in a new continent and very distant from London. French revolution is (at the very beginning) an attempt to transform already existing society, i.e. attempt to transform absolute monarchy in constitutional monarchy. Course of events leads to Terror and proclamation of republic and then to Empire. Most of these things were not intended and originally people wanted (inspired by the British constitutional model) constitutional monarchy. Russian revolution is inspired by Marxism and especially by its prophetic aspect (so-called historical law of inevitable arrival of Communism)
Explanation: American revolution wanted to create a society with kings, i.e. republican system. This is exactly what happened. French revolution intended to be a change for constitutional monarchy ...events took a bit different course. Russians acted on prophecy, they wanted a perfect Communist society without inequality but the result was totalitarian regime.
