Probably doesn't matter. Failed assassinations were far more frequent than successful ones. Wilson gets a bit of public sympathy from the attempt, but not enough (or permanent enough) to cut much ice with the Senate.
Incidentally, assassination is surplus to requirements. After his second collapse in October, Wilson was at death's door for several days, and Marshall was unofficially informed that the President could die at any moment. Should he do so, Maershall probably accepts al or most of the Lodge Reservations, and theToV is ratified. So there is a US delegate on the Council of the League at Geneva, though whether having him there makes a great deal of difference to later history is far from self-evident.