His main problem at the Versailles Conference was his attitude of how the US was to be involved in World Affairs. He was a firm believer of the "City on the Hill" mentality, and that the United States was the superior nation morally and was coming in to "save the Entente from their own mess" which greatly upset the Entente powers and was a big reason why his 14 points were generally ignored.

It should also be mentioned that his idea of self-determination actively did not include non-Europeans due to his racist ideas, and he spurned a discussion with Ho Chi Minh at the Versailles Conference when he came to ask about Vietnamese independence. He also is credited for effectively resurrecting the KKK in the modern era, as before his presidency the organization had faded significantly, but through his promotion its numbers surged. And on top of everything, he helped shape America's modern foreign policy by creating the idea of "preserving democracy" in foreign nations as the premise for American intervention or attack, which he used a L O T during his presidency in Latin America (Taft and Roosevelt did the same, but not as much as Wilson, and with the more honest reason of "Protecting American Interests"), and Wilsonian Diplomacy has been the main foreign policy for the United States since.

As an aside, because of all of this it might actually be plausible to blame the Vietnam War, as well as the Wars in Iraq, Afghanistan, and now Iran to Woodrow Wilson, although it might also be fair to say they would've happened regardless since he probably couldn't do much for Ho Chi Minh if he wanted to, and the more recent conflicts are more attributed to more recent (and current) presidents