I think that it was really not possible for the Continental Army to defeat the British Army in Navy. In a conventional war, much as the French and Indian War had been between the French and British armies. The most dire threat to the survival of the American Republic is when the American army has been defeated in Long Island,. Washington starts with 12,000 troops; he ends up with 3,000.
Joseph Ellis, of Mt. Holyoke College and author of American Creation, talks about the triumphs and tragedies of the founding of the United States. His goal in the book and in this podcast is to tell a story for grownups rather than for children, where the Founders are neither saints nor evil white, patriarchal slave-holding demons. It is a nuanced story of triumph--a military victory over a seemingly unbeatable vastly more experienced army, the creation of the first geographically large republic, a nation without a state religion, a nation that creates a party system with a loyal opposition, a Constitution with the virtues of ambiguous sovereignty, and tragedy--the failure to resolve the slavery issue, and the tragic conflict with the Native Americans. Some of these outcomes were intended by the Founders, others emerged unintended.