Oops...
Even so, I dispute that. Germany was essentially starved and blockaded by Britain and France, and they had the limitless manpower reserves of their respective Empires to draw upon. Germany would have lost the war of attrition whether the US entered or not....
The problem for the Central Powers throughout WWI was that they were badly outnumbered; the growing probability of imminent war in the early 20th century led Germany to revise strategy and tactics. Knowing they’d be outnumbered perhaps four to one resulted in emphasis on sheer firepower. British and French armies were shredded by it, and the only reason they stayed in as long as they did was that they believed Germany and Austria were nearly out of manpower; this was in line with official propaganda, particularly in Britain, which insisted (even to this day) that German casualty and KIA rates were comparable, when they were not — until the US entered the war. The French actually figured out the problems with Allied tactics first, and the US (uncharacteristically of course) owes a great big thank you to France for helping train the AEF along the lines that would beat the Germans. Those French rifles they sold to us were POSes though. :’)