The English blockade was broken when the Eastern Front collapsed; the food stopped by the blockade was now available in Russia (especially the Ukraine). Again, I honestly believe that the surrender of Russia forced the US government’s hand because we realized there was simply no way for the Triple Entente to win anymore. Even if they weren’t crushed, they were done; the defensive positions favored the Central Powers (on occupied land), and Austria-Hungary was saved completely (not just keeping its minorities in line, but actually occupying Serbia since 1915). Turkish losses on the Arabian peninsula were minor in military terms, and again those could be changed with the troops freed up in southern Russia (Turkey’s primary battleground, involving their actual homeland rather than that of the Arabs to the south).
The British, French, Italians, Romanians, and whomever else got sucked into the conflict would never have been able to cope with the German (and Austrian) strength freed up when the Russian war effort collapsed. Just as in WWII, in WWI most of the German manpower was in the east, and on all fronts the Germans had their adversaries outgunned. The only thing that prevented a Central Powers victory was the American Expeditionary Force.