During the winter of 1776-77, the Continental Army suffered terribly at their winter camp in Valley Forge. What Prussian-born general trained the colonists how to fight better and survive in battle?
That would be General von Steuben, who was born in Prussia in what is now eastern Germany.
After a career in the Prussian army during the Seven Years' War, he was looking around for military employment in France when he heard the American Continental Army were looking for experienced soldiers.
As you can see at https://www.nps.gov/vafo/learn/historyculture/vonsteuben.htm , he came across the Atlantic as a volunteer, and was given the rank of Lt. General by mistaken translation from his credentials through French from the original German! He'd only been a Captain in the armies of Frederick the Great.
He standardized the drill of the Continental Army, and worked as quartermaster and Inspector-General particularly for Gen. Nathanael Greene in the South.