Even before February of 1778, when an alliance was established between US Congress and the French, France had provided unofficial support to the colonies with shipments of weapons. When the treaty with France was signed, the American Revolution became a world conflict. Spain entered the war against Britain on the side of France and the Americans. Though Spain did not provide aid directly to the Americans, its efforts to recover Gibraltar from Britain diverted the latter's resources, as did their attempts to recover part of Florida (which in 1783 reverted to Spanish control).
From early 1778, French involvement in the American Revolution was direct and extensive. The French provided both land and naval support: Rochambeau's army fought along with Washington's troops, and DeGrasse's fleet eventually bottled up the British at Yorktown in October of 1781, forcing the surrender of Cornwallis's army. This defeat led Parliament to initiate peace negotiations with the Americans; after six years of fighting, the British realized that the rebellion was farther than ever from being ended. The French had also provided direct cash support to the colonies during this period, and their military efforts in the West Indies had, like the smaller Spanish efforts, diverted resources from what the British were able to commit to resecuring control of the American Colonies. The Treaty of Paris in 1783 represented partial revenge for the French against the British for the huge French losses in the Seven Years' War twenty years earlier.