During this era, the United States made more progress towards its ideals at home than it did abroad.
If we define the WWI era loosely, it can embrace much of the Progressive Era. This was a time when America generally became more democratic. Americans got to elect Senators directly. Women got the right to vote. There were, of course, deviations from democracy in WWI and the Red Scare, but America was generally becoming more democratic.
Overseas, there was little such movement. The US did not push for democracy or for self-determination for the countries of Asia or Africa. It did not grant immediate independence to the Philippines. It did little to promote democracy in the world as a whole.