Patriotism was one major strength, since many of these colonist gave up, pretty much on everything they ever had. They gave up on their families,home, children, etc. they did all that just for their liberty.
What that's it?!
The French really were the ones to really help the colonists. Their hatred against the English made them support the colonists cause, especially after the battle of Saratoga which really made them want to support the colonists.
Shortage of Weapons
What are we going to do without muskets?
We can always use Bows and arrows!
George Washington was a great leader, he is one of the reasons of the victory of the colonists. Because he was very experienced and talented, that allowed him to be a great leader to the inexperienced colonists.
Shortage of Nourishment
One of the greatest weakness of the continental army was that they were always short on capable men, to fight in the war. It was so bad in fact, that George Washington had no more than 20,000 men at one time and place.
The Continental army was always short on gun and gunpowder was even more scarce. In fact, Benjamin Franklin suggested that it would be wise to arm the soldiers with bows, arrows, hatchets, and knives.