Along with 18 and 30, I say George Washington.
Today we know that the great man himself entertained doubts about the cause. With New England states cut-off, a British force to the south, with inflation exploding and with desertions, in 1780, he wrote in his diary, “We seem to be verging so fast to extinction that I am filled with sensations to which I have been a stranger till these three months.”
The French secretly offered the British terms involving their keeping New York, the Carolinas and Georgia, but the offer was rejected. King George III thought that the financial collapse would soon be followed by a military collapse. Yet, George Washington pressed forward (publicly) and the Americans soldiered on.
A second person who could be identified as indispensable is King Louis XVI. His loan of 1779 in silver (which arrived here the next year), along with an army under General Rochambeau and a navy under Admiral D’Estaing gave the Americans new impetus and were crucial at keep the British navy at bay, during the Yorktown campaign. Some people cite Dr. Benjamin Franklin for his role in securing this loan. But, let’s give the French their due. We’ve been repaying our debt to them ever since.
It was Admiral de Grasse who defeated the British in the battle of the Capes...the Battle of the Chesapeake. Louis XV’s minister of war was the first to come up with the idea of aiding the Americans against the British in order to weaken the British in their ongoing war with the French, LaFayette’s intervention with Louis XVI sealed Franklin’s efforts. Lafayette had equipped his own soldiers and purchased a ship to sail to America to aid the Americans...all at his own expense. He was nineteen years old. He was 20 when he was badly wounded at the Battle of Brandywine. He is buried at Paris under soil from Bunker Hill. The American flag flies at his grave.