What was the most important reason why Wilson’s opponents argued against the League of Nations? The League of Nations failed to achieve major territorial gains for the United States. The League of Nations might have forced the United States to become an international peacekeeper. The League of Nations failed to sufficiently punish Germany for its actions in the war. The League of Nations did not include enough of Wilson’s Fourteen Points.

The league of nations forced America to become an international peacekeeper

Explanation:

After the Great War, most of the US was reeling from its effects and the chaos it wrecked on the US economy, which gave rise to isolationism. This meant that large portions of the public would be opposed to the league of nations, as it would force the US to mediate future conflicts.

not sure might be he acquired the entire oregon territory from great britain