France provided a whopping 90 percent of the rebels' gunpowder. Let that sink in for a second. Without France, the entire American Revolution would have devolved into a bunch of dudes swinging their muskets as clubs within weeks.
Still, the most important French contribution to the revolution (or, if you're British, their ultimate dick move) was the least visible to Americans. As mentioned, the reason France pampered the Patriots was always selfish. They were out to weaken the British forces -- particularly their naval strength -- in order to take the fight to them, perhaps even conquer them. That's why, for much of the Revolutionary War, the British ships tasked with kicking America's ass had to survive 12 rounds with the French navy before they could even think of crossing the Atlantic. France gleefully fought the British, eventually teaming up with Spain, declaring a war, attacking from all sides, and even setting up an invasion force. In those battles, America's independence was a fart in the desert.
So, when the Colonial army was fighting for dear freedom, history books tend to conveniently forget that they did so with French money, equipment, and backup forces, while France and its other allies were busy pummeling the empire from every other side.