Which event occurred after the US senate failed to pass the treaty of versailles

The US didn't pass the Treat of Versailles, instead, in 1921 Congress passed a resolution called the Knox-Porter Resolution. It served as a formal end to the war with Germany. The United States also never joined the League of Nations, which was just one of the many reasons the leave would never achieve credibility or build power. It eventually failed in it's main goal, to maintain peace, because just twenty years following its founding, World War II broke out.

I believe the answer is The League of Nations was significantly weakened.

The failed to pass it due to some agreement that happened with Georges Clemenceau, the French Prime Minister at that time.

This lead to United states Choose not to join the league of nations and ending up in significant weakening of the league of nations