How did President Wilson lose the peace in World War 1?

We refused to join the league of nation. (??) That decision took place after the victory, ie some two years after the hope of getting peace without victory had been abandoned. Basically, "Peace Without Victory" got nowhere because neither side was willing to settle for it. Both sides were fighting the war on credit and looked to reparations from the defeated enemy to pay their bills for them. Nor would they call off the war without substantial territorial gains to make it look as if the carnage had "achieved" something. Wilson could, in theory, have coerced the Allies into accepting his terms, by stopping vital exports to them from the US; but he had no equivalent "lever" against the Central Powers, so this would have produced a German victory, not a compromise. Wilson did not want that any more than he wanted an outright allied win - maybe even less. Wilson's attempt to get a peace conference going in Dec 1916 came to nothing, and a few weeks later Germany declared unrestricted u-boat warfare, which, since it targeted neutral (including American) merchant ships as well as Allied ones, soon made US neutrality impossible to maintain. Once the US had declared war on Germany in Apr 1917, the idea of peace without victory was as dead as mutton.