My obligatory link to an answer I wrote on Wilson's shortcomings is here. Copying the relevant paragraph to this question:

I think it's important to note that the League of Nations was established after World War I - it's just that the United States never joined it as a member. There is some argument as to how much this is Wilson's fault over, say Senate Majority Leader and bitter personal opponent of Wilson Henry Cabot Lodge, but it's worth noting that Wilson did not involve any Senators in the Versailles treaty negotiations, and refused to countenance any amendments to the final treaty he presented to the Senate for approval. The treaty was voted down twice: in November 1919, and again in March 1920, the latter time the treaty failing to pass its two-thirds threshold by 7 votes (21 Democratic senators had sided with Lodge's "Irreconcilables"). Wilson's intransigence at the very least contributed to this historic rejection (the Senate had never failed to ratify a treaty before), and this arguably fatally weakened the international project he was committed to.

I'm very familiar with the story of "heroic Wilson tried to get the Treaty of Versailles ratified, and villainous isolationists stymied him, inevitably leading to World War II". It seems especially common in US history as taught in high school, in no small part because a lot gets compressed into a condensed teaching space.

I don't particularly buy it. In part because it overlooks the very real political faults and blunders. Wilson wanted a straight yes or no vote, and was more willing to go on a public whistle stop tour of the US to argue his point than he was to negotiate with Senators on the matter. This tour most likely led to his incapacitating stroke, although it seems likely he suffered smaller strokes while in Europe negotiating the Treaty.

A large body of Senators were uncomfortable with the Versailles Treaty as-is, specifically because the Treaty included joining the League of Nations and as a member committing to using military force should the League require it - a moderate faction of Senators wanted a rider added that any such military action had to be approved by Congress, and Wilson refused any such condition.

Anyway, one issue with this view is that it places the blame for the failure of Versailles squarely on the US (and specifically on the US Senate). Even for historians who think the Versailles Treaty was enforceable (like Margaret MacMillan) acknowledge that the will to enforce its ideals and terms just wasn't there on the British or French side. Other historians (like Stephen Kotkin) think the Treaty was always doomed because it was not negotiated with the Germans (whose entire political spectrum was therefore committed to overturning the Treaty terms) and completely ignored Russia, who wasn't even invited to the conference. Once those two powers regained strength, this line of thinking goes, the Versailles order was doomed.

Finally, thus view ignores that, at least at the time, contemporaries did not see Wilson's successors as isolationist. The Harding Administration, very specifically Secretary of State Charles Evans Hughes (whom Wilson had narrowly defeated in the 1916 election) actually had a string of foreign policy successes that contrasted strongly with the failure and then drift of the late Wilson years. Bilateral peace treaties were negotiated, signed and ratified with Germany, Austria and Hungary in 1921. Hughes hosted the Washington Naval Conference in 1921-1922 which froze naval expenditures on and sizes of capital ships, and set defined fleet sizes for Britain, the US, Italy, France and Japan. The Dawes Plan of 1924 (backed by Commerce Secretary Herbert Hoover), saw an end to the Ruhr Crisis, and a temporary solution to the reparations payments issue, in part through the loan of substantial sums from the US to Germany.

While isolationism and the breakdown of the international order would go hand in hand, those were more the products of 1929 on (in no small part related to the Great Depression), rather than an accurate understanding of US foreign policy in the 1920s after Wilson's second term ended.