The Germans Staff after the start of the Argonne Offensive put it rather brutally in one of their analyses:
The American Infantry is very unskillful in the attack. It attacks in thick columns, in numerous waves echeloned in depth, preceded by tanks. This sort of attack offers excellent objectives for the fire of our artillery, infantry and machine guns.
In 1989 Historian and Army Officer Rod Paschall analyzed what had happened to the AEF.
It had gone wrong. [in the Argonne]. Even in the best of conditions it was doubtful whether nine divisions could be supported over such a poor network of roads. The Americans were tied to a simple but inflexible plan that called for attacking on line, anchoring flanks with the advance of neighboring units, and keeping within the confines of divisional boundaries, a system that the Germans had learned to abandon long before.
... American doctrine was based on the 1917 Field Service Regulations, which were hardly revised from the prewar 1911 version. The manual specified that the attack should be conducted under the conditions of fire superiority , with advance achieved by infantry rushes. Fire superiority was to be gained by accurate rifle fire. For the Americans, the bane of Western Front attackers--the machine gun--was viewed as a "weapon of emergency". . .To be sure, artillery would assist the infantry, but the soul of an American assault was the rifleman.