The revolutionaries had several advantages, but most of them are merely vague conceptual ideas that can not be materialized into guns, money, or soldiers. .
The Patriots were fighting to protect their own homes and families, and to protect their own rights and liberty, which could work as a motivation force in battles. They will always give their all and sometimes that could scare off the outnumbered British soldiers. .
The American soldiers were fighting on their home turf, which enabled them to use different tactics against the powerful British troops. They rarely fought head to head in an open field. Instead, the Americans relied heavily on guerilla warfare. They would use the terrain such as hiding in tall grass and behind trees, or by digging ditches, which might seem cowardly and unfair to the British. But it certainly benefited the Americans greatly.
The conditions of victory were more favorable to the Americans. They merely wanted to avoid losing, unlike the British, who must achieve outright victory in a given period of time.
The Patriots also noticed all the enemies that British made during its previous wars. Taken advantage of that, Thomas Jefferson smartly drafted and issued the Declaration of Independence, formally declaring war against the British. It did not only serve as a morale booster, but it also explained to the world why they should help us, that this was not just some sissy arguments but to a point where a total separation was needed. With the help of almost the continent of Europe, our chance of defeating the powerful, but lonely British army seemed bearable. They also received selected competent officers from foreign countries to support the patriot cause. Lafayette, Von Steuben, and De Kalb became household names overnight.
Another often overlooked advantage for the Patriots were African Americans. They saw the war as a passport to freedom. Although sometimes dismissed by the patriot leaders, they made a big difference of the fighting in the last years of the war took place in the South.