Probably we would have still entered WWI. The Zimmerman note affected Texas, mostly, so the South would have certainly been interested in the fight. As well, unrestricted submarine warfare was crippling the Northeast industrial engine... Also I don’t believe a pacifist like Wilson would have been the North’s choice as president. A Republican would have been in office and would probably have been a war hawk, eager for the fight against the German Kaiser. Entry for the North’s war would have come much earlier than the spring of 1917 too—perhaps as early as 1915.
TR was a total Hawk on WWI.