Well, I'm late to this discussion as I'm in between grueling business trips, and all my books are still packed away since the house was remodeled, so i'll keep it brief as I'm exhausted.
The French had been providing secret aid to the Colonials for quite some time before actually making an official entry into the AWI. Money, muskets, and gunpowder were all covertly sent to the Colonists thanks to the efforts of people like Benjamin Franklin and Silas Deane. In all of the 13 Colonies, there was only one or two makers of gunpowder supllying the Continental Army and the various militias, only a fraction of what Washington needed. There is strong evidence indicating many of the American forces at Saratoga were using the French powders, and also many of them carried French muskets, which in turn helped to dispense the various muskets of different calibers being used beforehand.
Needless to say, the money France sent was invaluable in more than one way, since Washington's army could shrink or swell in numbers on any given day. He had to keep his army together and promising land west of the Appalachains wasn't going to motivate many of them to fight. I think it's important to remember, that many of the colonials at the time, especially those in the cities and towns were still for the most part, pro-Tory. In fact. even Washington and many of his generals still felt allegiance to the British crown even well after the rebellion began. I think the notion that the AWI was a widespread and popular rebellion from the onset is something of a school text book myth. I think that only after Saratoga, did the people begin to learn of the details and exploits of Colonial armies and support the revolution. It was then that the actions of the men and generals become famous and thus the many legends were born.
There were several mistakes the British made during the AWI, but in my opinion, the worse was their offer of freedom to the slaves in the South, a decision that turned an otherwise indifferent and even pro-Tory population dead-set against them. This set off all kinds of pro-tory and pro-independence militia actions in isolated areas of the south, most often with intense brutality and savagery. Some of the stuff I've read makes the Hatfield and McCoy battles look like Sunday picnics. I think had the British left the South alone, the war would have been fought almost entirely in the North. By opening a front in the South, everything began to unravel and the British soon lost control of the fighting. This was favorable to Washington dictating where battles would be fought in the future.
Most interesting to me is that when France entered the fray, there were battles between French and British forces in various locations around the world. One could conclude that the AWI was in fact a world war, the first of it's kind. And what if the British had won? Would there have been a "Commonwealth of America", or one very large Canada? I don't think the word "United" would have been allowed, given it has an independent connotation. What would have been the name of this new and large British colony? Had the continent remained British, would the South have given up it's slaves when the UK outlawed it? Maybe it isn't too far fetched to think that there could have been a war of independence between the Independence-minded South and the Commonwealth North.
One thing is certain: whether it was France or any other nation capable of sending large amounts of weapons and monies, the AWI would have been lost without this kind of foreign aid.