Why did the colonists rebel?
How and why did the revolutions occur?
What about after the revolutions?
Isn't that what the computer/internet is very useful for finding extensive writings about this subject and anything else you want to know. If I were you, I wouldn't be wasting the question here! (And it costs you points)
Search the Web "French Revolution American Revolution similarities differences"
Their greatest similarity is that they were both revolting.
The biggest single difference between the two was that the American Revolution wasn't in fact a revolution. It was a war of independence--and was actually the first (successful) war of independence of the colonial era, something in which we can rightfully take pride. But it wasn't a revolution. Revolutions involve important changes to politics, economics, and/or society, but we didn't have that.
Basically, during colonialism we had a native ruling elite topped by an elite sent there from the UK. With independence, we stripped away the British elite but kept our own. No major changes took place in society (except we drove off the loyalists of course). Politically, we kept the basics in place: each state was still ruled by a legislature and headed by a governor--and the rules for who could vote didn't change. Economically, nothing really changed either.