Answer: It weakened Wilson's support for a League of Nations.
Step-by-step explanation:
You did not include the speech in question however this should be the correct answer.
As a result of the Treaty of Versailles, a League of Nations was formed and even though it was President Woodrow Wilson's idea, the US did not join because Congress was opposed to it so the speech in question is probably a speech that weakened support for the League of Nations.
Option B is wrong because the Senate did not abandon isolationism after WW1.
Option C is wrong because the US did not engage in aggressive actions to curb future dictators and the US did not establish an alliance with Britain as a result of the Treaty of Versailles.