It's seems most of what is now the Western world would have regarded the Founders as far to the left of their monarchies. On the other hand the French Revolution had just happened...
The French Revolution was some time in the future when the "founding fathers" were strutting their stuff.
The "founding fathers" were generally considered to have begun their work with the American revolution, starting in 1775 (though with some build up before), and concluded with the US constitution in 1789.
The French Revolution did not start until 1789. So, it had not "just happened" during the period of the founding fathers. It was still to come.
The French revolution ended up being far more "liberal" or "radical" than the American Revolution.
How "liberal" were America's "founding fathers"?
Not that universally liberal. Some might have been called "conservative", in that they were trying to conserve what they perceived as "the traditional rights of Englishmen" which they had enjoyed previously, but which they thought were being eroded.
Of course some were "liberal", and the abolition of slavery in some of the Northern states during the Revolutionary period is evidence. Meanwhile, the continuation of slavery in the Southern states is evidence that not all the "founding fathers" were particularly "liberal".