You should both read up on the history of the French Revolution, as well as the definition of the word "conceived". Yes, the parent was off in calling out the French Revolution specifically, but the actual statement made was spot-on.
The American Revolution was, in fact, built on earlier and contemporaneous ideas, found in myriad writings of mostly non-American Enlightenment thinkers who had been working out various new, altered, subversive, or otherwise novel ideas, studies, and classifications in political theory (among other topics) for nearly 125 years before American founders built upon them in both the Articles of Confederation and the US Constitution. A basic review of political theory in the Age of Enlightenment would both confirm for you the correctness of the parent's statements (despite the errant inclusion of the French Revolution), as well as help you see exactly where the American Revolution got the whole of its ideas. America's founders very much imbibed on the Enlightenment, particularly works of political theory.
The French Revolution was not in any way "conceived of" as a result of the American Revolution. Instead, it had been growing in its own specifically French/European manner among the salons and their philosophes, and was quite in step with the march of Enlightenment across much of Western Europe. Ultimately this was brought to a head when, seeing that the Americans' disregard for English rule was something they, too, could emulate in order to bring Enlightenment ideals to practical fruition in France, shit got started in the Estates-General in May 1789 (just two months after the Constitution replaced the Articles of Confederation, bringing the fully Montesquieu-esque political system into reality).
I apologize if I seem overly pedantic, but when you call out someone to check a timeline based on two words in an otherwise sound comment that added something to the discussion, you should at least ensure you have your own timeline correct--particularly if you are going to be bandying about the idea that Historical Event X "was not even conceived of until after" Historical Event Y. History rarely works like that, especially when it is happening but a handful of years apart.
Ultimately, what Abbé Sieyès said in his famous pamphlet, "What is the Third Estate?", is so applicable to both revolutions as to further indicate that a revolutionary wave was both forming and interacting on both sides of the Atlantic (trans-Atlantic intellectual and cultural history is an eye-opening field of study):
"What is the Third Estate? Everything. What has it been until now in the political order? Nothing. What does it want to be? Something."
The Americans espoused the same sentiment. Neither the American founders nor the Estates-General were owners of that idea, though. They both took it from 125 years of hundreds of intellectuals hammering it out.
EDIT: Formatting & a couple extraneous words.