What country was an ally to the US' ally during the American Revolution?

At the beginning, no one. However, after the Battle of Saratoga, the French began to pledge economic and naval support, along with limited military assistance. Towards the end, when British defeat was iminant, the Colonists were "joined" by the Spanish and The Netherlands. The reasons joined is in quotes is because they really offered next to no assistance, and just took the side of the colonists to gain trade rights from Britain.