Where and when did the US troops break the stalemate on the western front?

U.S. troops helped break the stalemate on the Western Front during World War I primarily in the Meuse-Argonne Offensive, which took place from September 26 to November 11, 1918. This massive operation involved American forces pushing through German defenses in northeastern France. The offensive contributed significantly to the weakening of German positions and ultimately played a key role in leading to the armistice that ended the war.