Yeah, I'm aware of the Wilson mediation efforts. AFAIK, though, they didn't actually have very much success because both sides still believed that they could win this war. Maybe if the US would have remained neutral, though, then the Entente would have become more willing to negotiate by late 1917 or early 1918 due to their much more dire financial situation by then.
Wilson had already laid the framework for exactly that in November; the Fed issued a note that non-collateral supported loans could no longer be issued and the Entente was due to run out of that in months. USW at the last second snatched ultimate victory away, as it forced the U.S. to rescind this policy in February. It was that close.