Unlike the earlier commentators, I think the USA could "lose" World War I if the German Spring and Summer offensives succeed, despite the participation of American soldiers. Keep in mind that American units would have been committed earlier if things got more desperate. If France throws in the towel, its hard for American units, who depend on the French army to train and for the most part to equip them, to remain in France. Well its less likely that Britain is the one to ask for an armistice, if they do so the French will as well, despite American participation.
The Americans will be represented at the peace conference but will be ignored. Wilson will be even more discredited than IOTL as will the Democrats. The Republicans made big gains in 1918 and 1920 IOTL and were the dominant party in the 1920s. ITTL they will be more dominant and Wilson could well be the first President impeached and removed from office, especially if he still has his stroke. The Democrats could also be replaced outside the southern states by a progressive party (IOTL one did contest the 1922 and 1924 elections but didn't have enough success to become the alternative to the Republicans). Also FDR is less likely to be the Democratic vice presidential nominee, his service in the Wilson administration is not a positive, and Thomas Marshall might be the nominee if Wilson is removed and may pick a different running mate.
Basically the Americans would have mobilized a big expeditionary force, contributing to an influenza outbreak, and sent it to Europe only for it to have no effect on the war's outcome. People would come to the opinion that this was done on behalf of the British much more than IOTL and there would be more isolationist sentiment and more anglophobia. It wouldn't help that the Americans also allied briefly with Russia only for it to go communist (incidentally in any "Germany wins World War I" timeline there is probably no Nazi Germany so there is even less reason for the USA to get involved in European matters.
Prohibition was partly sold as supporting the war effort and is less likely with the war discredited. The Great Depression is also different, it probably comes earlier, but it will be different. Another factor that comes into play that the Dominions reduce their ties to Britain much earlier and probably more so than IOTL.