What role did european nations play in the american revolution? how did their involvement affect the course of the war?

Because the French was a colonial rival of the British, they were looking for ways to boost their reputation while undermining Britain's.  France supplied the States with arms, uniforms, munitions and supplies. They also sent troops and the navy. Their biggest contribution came during the battle of Yorktown. The Germans helped the British. They were a help to England in battles fought around New York, but they lost the Battle of Trenton.